How and why do travel patterns vary by gender and parenting status?

Mon 1 July, 2024

A lot of published transport analysis – including on this blog – has been gender-blind. Yet there are quite significant differences in travel patterns between men and women, and also between parents and non-parents. Advances in equality of opportunity have not eliminated these differences.

This post goes all-in with disaggregating a wide range of available data on transport behaviour on gender and parenting status in Melbourne, and explores some factors likely influencing these behaviours.

I will look at trip rates, trip chaining, time spent travelling, destination distance from home, distance travelled, travel to the central city, time of day, mode splits, use of different modes, trip purposes, and radial-ness of travel. I’ll also look at explanatory variables including main activity, occupation, employment industry, access to independent private mobility, and geographic distribution of home and work locations. Yeah that’s a lot, but don’t worry, there is a summary towards the end.

There’s also an interesting aside about dwelling bedroom counts around train stations.

This post is mostly focussed on working aged people (approximated by the age range 20-64), as children and seniors are likely to have different travel patterns again. And for the purposes of this analysis, I’m classifying people as “parents” or “parenting” if they live with their children – i.e. they are likely caring for their children (although some might have relatively independent adult children living with them). Parents whose adult children have all left home will be classified as other males/females.

About the data

I have access to very detailed household travel survey data for my home city of Melbourne for the pre-pandemic years 2012-2018, so that’s my primary source (officially VISTA – the Victorian Integrated Survey of Travel and Activity, get data here). It covers all types of non-commercial travel by residents, on all days of the year. Of course that data is pre-COVID and things will have changed somewhat since then but rich post-COVID data is not yet available.

I’m aggregating outputs to differentiate school weekdays, non-school weekdays, and weekends (I have excluded data for public holidays).

The VISTA data reports on binary gender, so unfortunately I can only cover males and females. That said, even if it did include more diverse gender categories, it would likely be very difficult to get statistically significant sample sizes for non-binary gender groupings.

There’s no special treatment required for same-sex parenting couples – they each count as mums or dads based on their reported gender.

Here’s how prevalent the different gender + parenting classifications are by age band in the weighted VISTA data for 2012-18:

The survey weightings don’t quite lead to a perfectly balance between genders across all age bands.

Parenting was most common amongst those aged 40-49 (almost three-quarters), and lower prevalence in younger and older age groups (under 8% for those aged 20-29).

Curiously there was a slight uptick in parents living with their children for ages 80+, which might be elderly parents living with – and being cared by – their adult children.

Across the approximate working aged population (20-64), parents accounted for 45% of the population.

In some sections I’ve also used ABS Census data from 2016 and 2021. This data is segmented slightly differently, with parenting being indicated by whether the person does unpaid work to care for their own children (so might exclude parents with relatively independent adult children living with them). Unless noted otherwise, it includes people aged 15+, and journey to work data only includes those who travelled to work and reported their travel modes.

Let’s get into it..

Trips per day

For this analysis a trip is travel between two places where a purposeful activity takes place, and may involve multiple trip legs (eg walk-bus-walk-train-walk).

Mums easily made the most number of trips on school weekdays, but dads made more trips on weekends than mums. Trip rates were higher on weekends for all person classifications except mums.

Trip chaining

I’ve heard much about women doing a lot more trip chaining – where a person leaves home and travels to one activity, then one or more other activities, before returning home. For example: home to school drop-off to work to school pickup to home.

As a simple measure of trip chaining, I’m counting the number of trips that don’t have an origin or destination at a place of accommodation (places of accommodation almost always being the survey home). I am aware of other definitions of trip chaining that only count where there is a short activity between trips but that would be require much more complex analysis.

As expected, mums were doing a lot of trip chaining on school weekdays, but curiously dads weren’t that far behind. And in the school holidays and on weekends dads were doing more train chaining than mums (perhaps to give mums a break?).

Trip chaining was much less common on weekends for all groups.

For mums the most common trip type not involving travel to or from home was between work and pick-up or drop-off of someone (most likely between a school and a workplace). A long way behind was travel between work and shopping, pick-up/drop-off someone and shopping, and between two pick-up/drop-off someone activities.

For dads the most common trip type not involving travel to/from home was between two work-related activities, closely followed by between work and pick-up / drop-off someone, and then between work and social activities.

So mums’ trip chaining was dominated by pick-ups and drop-offs of people, while dads’ was not.

Time spent travelling

There’s not a huge variation in median travel time per day between person groups, but dads had the highest on weekdays and mums generally had the lowest. Note that reported travel times were very often rounded to multiples of 5 minutes hence most of these medians are also multiples of 5.

Technical note: I have created a chart with average travel times and the numbers were higher but the shape of the chart was almost identical so I’m not including that here.

Travel distance from home

So were dads travelling further from home? I’ve calculated the straight distance between the home location and all travel destinations, and this chart shows the medians:

Dads sure did travel further from home on weekdays (particularly on school holidays when they might not be doing school drop-offs / pick-ups), with mums generally staying much closer to home.

Curiously, other males also travelled further from home than other females, so this pattern appears to be related to gender to some extent.

There was a lot less variation on weekends, with people generally travelling closer to home, as you might expect.

Daily distance travelled

Let’s broaden that out to median total distance travelled per day:

Dads generally travelled further on all day types, and mums the least. Everyone generally travelled less on weekends, and to some extent during school holidays (compared to school weekdays).

Travel distance to work

We can use ABS Census data to understand the on-road distance between home and workplaces, including for 2021. This data is for the working population aged 15+, and differentiates people based on whether they are caring for their own children (which is slightly different from living with their children).

The median distances to work were highest for dads at around 15.4 km for dads, followed by 11.9 km for mums, 11.7 km for other males, and 10.2 km for other females.

Travel to/from Central Melbourne

Public transport has its highest mode shares for travel to/from central Melbourne, so how did that vary by sex and parenting status? (for this analysis I’ve defined central Melbourne as the SA2s of Melbourne, Docklands, Southbank, and East Melbourne – on 2016 boundaries).

Before you get too excited about the differences, it’s worth pointing out all the proportions are small. The vast majority of people in Greater Melbourne don’t travel to central Melbourne on any given day. And of course people who lived in central Melbourne had many of their trips counted in this chart.

Sure enough, on weekdays dads were much more likely to travel to central Melbourne, and mums were least likely (although it was higher in the school holidays). On weekends, non-parents were much more likely to travel to the central city than parents (a fair bit of socialising by younger independent adults, no doubt).

Time of day of travel

The following chart shows the share of trip start times across the day for the different person types, and different day types:

Technical note: due to smaller sample sizes, weekend travel has been aggregated into 2-hour intervals. Weekdays have been aggregated into 1-hour intervals.

You can clearly see that on school weekdays, mums are doing a lot of travel between 8 and 9am, and between 3 and 4pm, which obviously relate to school start and finish times. In the school holidays, mums are doing a lot more travel through the interpeak period, probably reflecting parenting activities for kids not at school.

On school days, trips by dads started earlier and finished later than mums. But during school holidays dads made a smaller proportion of their trips between 8am and 9am, suggesting they also had a significant role in school drop offs in the morning.

During the weekday inter-peak period dads were less likely to travel than mums (except around lunchtime). Other females had a small peak in travel around 5-6pm, which is probably related to them being more likely to work full time.

On weekends it seems dads were slightly more likely to travel in the morning compared to mums who were slightly more likely to travel in the afternoon.

Did mum or dad take the kids to/from school?

We’re seeing some pretty strong themes related to the school peaks. It is possible to filter for trips to pick up or drop off someone from a place of education on school weekdays and then disaggregate between mums and dads. I’ve split this analysis into an AM peak, a PM school peak (2-4pm), and a PM commuter peak (4-6pm) – as there were significant numbers of pick ups later in the afternoon – presumably following after-school care.

Mums did the bulk of school drop offs and pick ups at all times of day, particularly in the PM school peak. In the PM commuter peak, dads share of pick ups rose to 35% – no doubt related to the ability to do these pick ups after a full-time day at work.

What types of adults are using modes at different times of day?

For this question I have limited analysis to school weekdays, aggregated all of public transport to one group, and aggregated vehicle drivers, passengers, and motorcyclists into “vehicle” to overcome issues with small sample sizes. I’ve included the proportion of the working aged population sample on the right-hand side for ready reference.

In general, parents were over-represented in vehicles in peak periods, mums were over-represented in the interpeak in vehicles, and parents were under-represented in public and active transport at most times of day.

The peak periods saw more public transport trips by dads than mums, while the roads (and footpaths) saw a lot more trips by mums than dads.

Early morning travel was predominately by males (76%), while females were slightly more prevalent in vehicles during the interpeak (60%). Reported walking trips skewed female at all times of day.

However if we look at travel time, rather trip counts, we get a slightly different picture:

Dads spent more time travelling than mums in peak periods on both public and private transport, but much less time than mums in the inter-peak.

Mode split

Here’s how it looks for travel in general:

Mums were the least likely to use public transport (especially on the weekend), closely followed by dads.

Non-parents had the lowest private transport mode share (although still a majority mode share), and were most likely to use active transport.

Here’s overall mode shares of journeys to work (Greater Melbourne 2016), which I’ve disaggregated for workplaces inside and outside the City of Melbourne area (as workplace location has a massive impact on mode shares):

Parents were much more likely to use private transport across the geographies and sexes. Of those working outside the City of Melbourne, parents also had about half the public transport mode share of non-parents.

Men were much more likely to cycle to work than women, and dads were more likely to cycle than other men.

Here is a look at private transport mode shares by distance between home and work, gender and parenting status:

The difference in private mode share between parents and non-parents was largest for journeys up to 10 km. Mums had the highest private mode share for journeys 1 to 20 kms. For journeys over 25 km, sex became more influential than parenting status with men more likely to use private transport.

Another curiosity here is the very short journeys (less than 0.5 km) where men were much more likely to use private transport than women (regardless of parenting status) – for what is probably a walkable distance for most people. Are men more lazy when it comes to short walks to work? And/or are men more likely to need their car at work?

I have previously also analysed public transport mode share by age and family position. I’ve reproduced that analysis here:

For ages 35 to 59, mums generally had lower public transport mode share than dads. Younger non-parenting women had higher public transport mode shares than younger non-parenting men.

Here’s how it looks for 2016 journeys to work (I’m not using 2021 data because of COVID lockdowns):

Female public transport mode share was signficantly higher than males for most ages – except for those typical parenting years between their late 30s to early 50s. Younger adults were much more likely to work in the inner city, and even more so for females. For more discussion on this, see Why are younger adults more likely to use public transport? (an exploration of mode shares by age – part 1)

I’ve also split this by sex and parenting status and analysed the changes between 2006 and 2016 (analysis lifted from: Why are young adults more likely to use public transport? (an exploration of mode shares by age – part 3))

Note there is a very different Y-axis scale for City of Melbourne and elsewhere.

There were a few really interesting take-aways:

  • Public transport (PT) mode shares increased over time for almost all age bands, work locations, and for parenting and non-parenting workers.
  • Parenting workers mostly had lower public transport mode shares than non-parenting workers of the same age, except for:
    • dads over 30 who worked in the City of Melbourne,
    • mums in their early 30s who worked in the City of Melbourne in 2016, and
    • mums and dads in their 50s who worked outside the City of Melbourne (who had low PT mode shares around 4-5%, similar to non-parenting workers of the same age)
  • Public transport mode shares for journeys to work in the City of Melbourne mostly declined with increasing age between 20 and 50, regardless of parenting responsibilities.
  • For people who worked outside the City of Melbourne, the mode share profile across age changed significantly over time for young adults. In 2006 there was a steady decline with age, but in 2011 PT mode shares were generally flat for those in their 20s, and in 2016 PT mode shares peaked for women in their late 20s (and also had a quite new pattern for dads in their 20s).
  • For parenting workers who worked outside the City of Melbourne there was actually a slightly higher PT mode share for those over the age of 50. Parents over 50 might have older children who are more independent and therefore less reliant on their parents for transport. This might make it easier for the parents to use public transport. However this trend did not hold for dads in 2016.
  • PT mode shares for non-parenting women increased slightly beyond age 55 for all work locations. This will include women who were never parents, as well mums with non-dependent children so might again reflect a small return to public transport once children become independent. It may also be influenced by discounted PT “Seniors” fares available to people over 60 who are not working 35+ hours per week.

Mode split of public transport use

Which modes of public transport were the different person classifications using in Melbourne? Sufficient survey sample is only available for school weekdays, and it’s important to keep in mind that trams dominate inner city radial on-street public transport in Melbourne (unlike most comparable cities where buses dominate this function). This chart adds up all trip legs so there is no data loss with multi-modal public trips:

Unfortunately this data doesn’t line up with reported public transport patronage for the same time period (below), suggesting that tram travel may be under-reported in VISTA (although the above chart is filtered for persons aged 20-64):

Biased as the VISTA data might be towards certain modes, it still suggests dads were more likely to be using trains and least likely to be using buses.

I’ve also looked at use of public transport in journeys to work for 2016. Workers can report up to three modes of travel, and I’ve extracted counts of workers who used each of the three main modes of public transport in Greater Melbourne (note: people who used multiple public transport modes will be counted in multiple columns).

Parents (who travelled to work) were much less likely use bus or tram to get to work than non parents. But the story is bit different for trains: Dads were slightly more likely to commute by train than other males, while mums were less likely to commute by train than other females. This might be related to where mums work – more on that soon.

Mode use by sex and parenting

We can flip the mode-split charts around to look at the composition of adult users of different travel modes:

Technical Note: there’s insufficient sample of tram, bus, and bicycle travel on non-school weekdays and weekends so those are not on the chart.

Trams, buses, private vehicles, and walking generally skewed female, while trains and particularly bicycles skewed male (except weekend trains).

Mums were under-represented on all modes except private vehicles where they were significantly over-represented. Mums were least represented on bicycles.

Dads were under-represented on trams and buses, and over-represented in vehicles, and on bicycles.

Non-parents were over-represented on trains and trams, and walking on weekends.

There were many more dads than mums on trains on weekdays, and many more mums than dads travelling in (private) vehicles on school weekdays (but not so much on weekends and school holidays).

Trip purposes

We want to know the purposes of people’s travel, but actually purpose can only really be attributed to the activity before and after a trip. For this analysis I’ve used the trip destination purpose as the trip purpose, and I’ve excluded trips where the destination was home (as that would be close to half of trips and not very interesting). Also keep in mind that trips can also vary considerably in length and duration.

On weekdays, significantly more trips by males were work-related. Mums had a standout different pattern on school weekdays with many more trips being about someone else’s travel (particularly school children) and much less often being work-related (or should we say “paid work”-related).

During school holidays, about 1 in 5 trips by mums were about other people’s travel. But on weekends dads were doing slightly more trips that are about other people’s travels (perhaps to make up for them doing less of such trips on weekdays?).

On weekends social and shopping trips were much more common than work trips, as you’d expect.

Radial-ness of travel

A while ago I looked at the radial-ness of travel – that is the difference in bearing (angle) between a trip aligned directly to/from the Melbourne CBD and the actual alignment of the trip. Trips generally skew towards being radial, reflecting the importance of the central city, and just generally the shape of the city. Previously I’ve disaggregated by age, sex, and many other variables.

So how does radial-ness vary across sex and parenting status?

On weekdays mums were the clear outlier, with substantially fewer radial trips and more non-radial trips, likely including many trips to/from schools and other caring destinations.

Weekend travel was a fair bit less radial in general, and again mums had the least radial travel of all person groups.

Okay so that’s a lot of ways we can compare travel patterns by sex and parenting (let me know if you think I’ve missed any other useful breakdowns). Now…

What can explain these differences?

A lot of the above data is probably unsurprising, because males and females, and particularly mums and dads, generally have different levels of workforce participation and caring responsibility, amongst other differences. What follows is an examination of potential explanatory variables for the different travel behaviour observed.

Main activity

First up, main activity as captured by VISTA:

Dads were most likely to be working full-time, and mums least likely to be working full-time. Mums were much more likely to be working part-time or “keeping house”.

As an aside: I actually find “keeping house” to be a bit devaluing of parents (usually mums) who dedicate much of their time doing the critically important work of raising children. And I know from personal experience it’s pretty hard to actually “keep house” when you have young children who need active engagement across most of their waking hours. No doubt others falling in the “keeping house” category might be caring for other adults or the elderly. Is it time for a caring-related category?

Curiously non-parenting females were much less likely to be working full time than non-parenting males. Perhaps non-parenting females were more likely to be doing some caring for others not living with them? Perhaps some mums decide to stay working part-time after their children move out? Or it might be something else?

We can break the analysis down further by age:

Technical note: Data isn’t presented for mums and dads aged 20-29 due to insufficient survey sample.

Curiously, dads were less likely to be working full-time with increasing age, while mums became slightly more likely to be working full-time at older ages (as children get older and require less supervision?).

Occupation (employment)

We call drill down further by looking at employment occupations:

Mums were much less likely to be in the workforce than dads, but curiously had almost the same proportion of professionals (perhaps reflecting women’s slightly higher levels of education, on average).

Men were more likely to work in occupations where public transport is probably less competitive, including technicians, trades workers, labourers, and machinery operators and drivers (with likely exceptions for central city work sites).

Employment Industry

There are also notable differences in employment industries by sex and parenting:

There are probably no great surprises in the above chart, with men much more likely to work in construction, information media and telecommunications, manufacturing, transport, postal, and warehousing, and women much more likely to work in education, training, health care, and social assistance.

Access to independent private mobility

Does the ability of people to drive themselves around in private vehicles differ by gender and parenting status? And could this explain their different travel patterns?

For this analysis, I’ve re-used the following household classifications from a previous post:

  • No MVs – no motor vehicles,
  • Limited MVs – fewer motor vehicles than licenced drivers, or
  • Saturated MVs – at least as many motor vehicles as licenced drivers.

I’ve also classified individuals as to whether or not they have a “solo” driving licence (i.e. probationary or full licence, but not learner’s permit).

I’ve then combined these two dimensions (except for people in households with no motor vehicles as driver’s licence ownership is largely immaterial for this analysis).

There were small differences between mums and dads, with mums slightly less likely to have a solo driver’s licence than dads (95% v 98%), mums slightly less likely to have independent private mobility (75.5% v 78.6%), and mums slightly more likely to live in a household without any motor vehicles (1.7% v 1.0%). These slight differences might suggest mums would have lower private transport mode shares than dads, but we’ve actually seen above that the opposite is true. Therefore access to independent private mobility is unlikely to explain much of the differences in travel between mums and dads.

There weren’t substantial differences between non-parenting men and women, other than non-parenting men having slightly high solo licence ownership (91% v 88%).

Parents were more likely to have a solo driver’s licence than non-parents, and over three-quarters lived in a household with saturated motor vehicle ownership. Access to independent private mobility aligns strongly with parents’ much higher private transport mode shares, and is probably considered essential for parents in most parts of Melbourne.

Indeed, we can also break this down by geography – using a simple inner/middle/outer disaggregation of Melbourne:

For all person categories there’s a strong relationship with distance from the city centre, with significantly lower levels of motor vehicle ownership in the inner areas. However solo licence ownership was very high for parents even in the inner suburbs (94% of mums and 98% of dads).

86% of dads and 87% of mums in outer Melbourne lived in households with saturation motor vehicle ownership. However, 5% of mums in the outer suburbs didn’t have a solo licence, which could make getting around quite challenging, and highlights the importance of quality public transport services in these areas.

Around 14% of non-parents in the inner suburbs lived in households without motor vehicles.

Where do parents tend to live?

It probably won’t surprise many readers to hear that parents made up a much larger share of the residential population in the outer suburbs, particularly urban growth areas:

But if you look closely, you’ll also see quite low proportions of parents along train lines, tram lines, and the public transport rich inner suburbs.

In fact, it’s possible to examine the type of households per dwelling by distance from train stations (I’m excluding areas within 3 km of the CBD).

Technical notes: I’ve calculated straight distance between SA1s centroids and their nearest train station points as per GTFS data in May 2024. The only significant change in train stations between August 2021 and May 2024 was the merger of Surrey Hills and Mont Albert into Union Station in 2023. So it’s not perfect analysis but I’m also not interested in precision below 1% resolution. I’ve also excluded unoccupied and non-private dwellings.

Dwellings close to train stations are significantly less likely to contain parents.

Is this because parents cannot afford family-friendly dwellings near train stations? Is it because dwellings near train stations are less family-friendly? Or is it because many parents like to build their own home on the urban fringe? Or some combination of these?

Well, the census tells us how many bedrooms there are in most occupied private dwellings, and the following chart shows the relationship between number of bedrooms and distance from train stations (again, excluding areas within 3 km of the CBD):

Sure enough, dwellings near train stations generally had fewer bedrooms.

And we can also use census data to show the relationship between number of bedrooms in a dwelling, and whether the household includes parents + children:

Over 90% of parenting households had three or more bedrooms, and half had four or more bedrooms. But almost half of all dwellings within 1 km of a train station had two or fewer bedrooms rendering them not very family-friendly.

Just to take it slightly further, I’ve put all three dimensions on one chart and this shows that dwellings close to stations with three or more bedrooms were slightly less likely to house parenting families:

I think the lower availability of family-friendly housing near rapid public transport is quite likely to be contributing to lower public transport mode shares for parents, particularly as there is a clear relationship between public transport use and proximity to rapid transit stations (see: Are Australian cities growing around their rapid transit networks?)

That said, there may also be an issue around whether many families can afford three-bedroom homes close to train stations as they often have less than two full-time incomes supporting three or more people. Might young professional couples with no kids and/or share houses of young professionals be better placed to compete for this housing?

Where do men and women work in Melbourne?

Could differences in journey to work mode splits be explained by differences in workplace location?

Here’s a map of gender balance by workplace location across Melbourne for 2021 at destination zone geography (DZs) (sorry not all outer suburbs included on the map as I didn’t want to lose the inner area detail). Blue areas skew male, orange areas skew female.

Anyone with knowledge of Melbourne’s urban geography will instantly see large industrial areas shaded blue, and plenty of orange in most other places.

These skews follow industries with male and female dominant workforces. In fact, I’ve manually done some rough grouping of destination zones where there is a clear dominant land uses (not exhaustive but results should be fairly indicative), and here is the sex breakdown by land use type:

Industrial areas and Melbourne Airport skewed heavily male, while hospitals and large shopping centres skewed female. Universities skewed female, and the CBD and surrounding areas slightly skewed male.

What about parenting? Something to keep in mind is that 43% of the working population were living with their children.

Parenting workers were seen more in the middle and outer suburbs, which is also where parents skewed as a home location, so there’s undoubtedly a relationship there.

Here’s the parenting breakdown by dominant land use classification:

Parents were under-represented in major shopping centres (I’m guessing a skew to younger employees), but also to a small extent universities and the central city. Parents were slightly over-represented in hospitals, Melbourne Airport, industrial areas, and the rest of Melbourne.

Another way to represent this data is looking at the distribution of workplace locations by distance from the Melbourne CBD:

Probably the biggest stand-out is that mums skewed towards suburban employment locations, while non-parenting females were more likely to be working closer to the city centre.

The distribution of workplace distance from the CBD for males only differed slightly between those parenting and non-parenting. Dads were less likely to be work between 2-10 km from the Melbourne CBD than non-parenting males.

Employment density

I’ve previously shown that private transport mode shares are generally much lower in areas with higher job density (likely due to higher car parking costs and increased public transport accessibility). So do mums/dads/others typically work in areas of lower or higher job density, and could this explain differences in their mode splits?

To answer this I’ve calculated an aggregate weighted job density of the areas in which each category of person tends to work. How does that work? Well to start with I’ve calculated the job density of every destination zone in Greater Melbourne. I’ve then calculated a weighted average of these densities, where the density of each destination zone is weighted by the number of dads/mums/other males/other females working in that zone.

For females, those non-parenting generally worked in more jobs dense areas, compared to mums. This probably partly explains the lower public transport mode shares of mums.

For males it was the reverse – dads generally worked in more jobs-dense locations.

Overall was only a tiny difference between men and women in aggregated weighted job density:

That was a lot of charts, can you summarise that?

The following table attempts to highlight key variations from the overall average for different types of adults:

Type of adultTravel patternsDestination patternsMode split Explanatory factors
ParentsMore trips per person on weekdays.
More trip chaining.		Higher private mode share.Live further from public transport.
Lack of family-friendly dwellings near public transport.
Live in outer suburbs.
Higher car ownership.
MumsMore travel during weekday interpeak.
Highest trip chaining.		Travel closer to home.
Work closer to home.
Less radial travel.
Least likely to work in CBD.		Very high private transport mode share.Do most school drop offs / pick ups.
Least likely to work full time.
Less likely to work in job-dense areas.
DadsTravel longer distances.
Travel further from home.
More time spent travelling.		Travel further from home.
Work further from home.
More likely to work in CBD.		More likely to use trains.
More likely to use bicycles.
Most likely to work full time.
More likely to work in job-dense areas.
Non-parenting womenTravel closer to home.
Work closer to home.		Higher public transport use.More likely to work in job-dense areas.
Most likely to work in central city.

The explanatory factors in the right hand column will not be independent. For example, many parents probably find it infeasible to live near public transport, so they live further away and are more car-dependent.

What does all this mean for transport planning interventions?

I won’t say a lot on this topic (I tend to avoid policy prescriptions on this blog) but I will say I think some caution is required here.

One perspective might be that the proportion of males and females travelling on a mode at a particular time of the week will not change, and therefore interventions might predominantly benefit the existing user base (eg higher inter-peak public transport service frequencies might benefit women more than men).

However another perspective might be that interventions remove the barriers for one gender to utilise a mode of transport and might have significant benefits for the minority gender in the current user base. For example, significantly safer cycling infrastructure might encourage more women to cycle and lead to a more even balance between genders – indeed I’ve uncovered evidence about that on this blog.

So many mums driving kids to school!

One thing that really stands out to me is that mums do the vast majority of school drop offs and pick ups, and most of this travel is (now) happening by private vehicle. This is potentially impacting women’s workforce participation, and the traffic volumes are certainly contributing to road congestion. It might also be impacting women’s mode choices as school trips are generally more difficult on public transport, and mums do a lot of trip chaining. They might be using private transport for some trips mostly because those trips are chained with school drop-off/pick-ups.

What could you do to reduce private transport trips for school drop off / pick ups, and potentially also increase women’s workforce participation and public transport mode share?

  • Make interventions that increase the share of school students who travel to/from school independently by active or public transport
  • For school trips that are accompanied by a parent, encourage a mode shift towards active transport (realistically, public transport is less likely to be an attractive mode for many accompanied trips to school, unless it is on the way to another destination)
  • Provide at-school before-school and after-school care to enable both parents the opportunity to work full time (indeed government subsidies are provided in Victoria at least)

How might things have have changed post-COVID?

Unfortunately at the time of writing rich data is only really available for pre-COVID times.

A major change post-COVID is that many white collar professionals are now working from home some days per week, which has reduced travel to major office precincts.

I would not be surprised to see dads taking a slightly higher share of the school drop-off pick-up task as this can be easier to do on a work-from-home day. Might this have enabled women to work longer hours? There have also been higher child-care subsidies implemented recently that might also lift women’s workforce participation.

Indeed here’s a chart summarising female labour force status since 2012 (not seasonally-adjusted):

Technical note: I would have preferred to use seasonally adjusted or trend series numbers to remove the noise, but these data sets do not include counts for “not in labour force”

Following the major COVID disruption period around 2020-2021, women have been more likely to be working full time and more likely to be in the labour force. This might be partly related to new working-from-home patterns.

Hopefully more post-COVID travel data will be released before too long and I can investigate if there are any substantial shifts in the patterns between men and women, parents and non-parents.

Do let me know if you think there is more that should explored regarding the differences in travel patterns and explanatory variables for men and women, parents and non-parents.

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Posted by chrisloader

Why are young adults more likely to use public transport? (an exploration of mode shares by age – part 4)

Sat 13 January, 2024

I’ve been exploring why younger adults are more likely to use public transport, looking at data sets available for Melbourne. This fourth post in the series looks at the relationship between public transport mode share and income, socio-economic advantage/disadvantage, occupation, hours worked per week, and whether people are studying.

It concludes with a summary of the findings from the four posts in this series. For more detail about the data, see the first post in the series.

(note: I started writing this post quite a while ago – apologies I got distracted by new data releases including the 2021 census data)

Here’s an index as to which posts look at which factors (including many combinations of these factors):

  • part 1: age, sex, travelling to city centre (or not), workplace distance from CBD, education qualifications, home distance from CBD.
  • part 2: proximity to train stations, population density, job density, motor vehicle ownership, driver’s licence ownership.
  • part 3: parenthood, birth year, immigrant arrival year.
  • part 4 (this post): income, socio-economic advantage/disadvantage, occupation, hours worked per week, whether people are studying.

Income

Could income explain different levels of PT use by age, if older workers are earning more and therefore more able to afford to drive to work?

Well, do older adults actually earn more than younger adults? Here is the distribution of worker incomes by age group, split between people who work inside and outside the City of Melbourne, for the last pre-pandemic census (2016):

Apart from the few people still working in their 90s (presumably because they are making great money), income was generally highest for people in their 40s in 2016. Older working aged adults generally earnt less! This may well reflect the higher levels of educational attainment of younger adults (as we saw in part 1).

So the idea that older adults are driving to work because they are generally earning more just isn’t supported by the evidence.

The above chart also confirms people working in the City of Melbourne were much more likely to have higher incomes.

But is there a relationship between income and mode choice? The following chart shows public transport mode shares for journeys to work by both income bands and age.

Each line is for an income band, and you can see age-based variations in PT mode share for people within each income band. The biggest age-based variations were for people on lower incomes – with younger workers much more likely to use public transport than older workers.

There was less variation across age groups in public transport mode shares for people on higher incomes, particularly those working in the City of Melbourne.

Most of the higher income bands had high public transport mode shares for journeys to work in the City of Melbourne. The exception was the top band ($3000+ per week), many of whom probably have a car and/or parking space provided by their employer. Also, over 10% of people in the top income band walked or cycled to work which might be because they can afford to live close to work.

For those who worked outside the City of Melbourne, PT mode shares were generally higher for younger workers and those on lower incomes.

Here’s another view of the same data, with income on the X-axis and different colours used for different age ranges:

On this chart you can see income not having a strong relationship with PT mode share within many age groups. For those under 30, PT mode shares generally declined with increasing income. For workers over 40, mode shares slowly went up with income in the City of Melbourne, and declined slowly with increasing income for those working outside the City of Melbourne.

Overall it looks like age probably had a stronger relationship with PT mode shares than incomes, although both factors are relevant.

Here’s a chart that simply shows journey to work mode shares by personal income (regardless of age):

However, personal income is not necessarily the best measure here to measure the impact of income. A person living alone earning $2000 per week has more to spend on their transport than a person earning $2000 per week but also supporting a family. The ABS calculates a metric known as household-equivalised income, which considers total household income in the context of household size and composition. Unfortunately household equivalised income isn’t readily available for journey to work data which includes work location, hence why the above analysis uses personal income. But it is available if I’m only concerned with where people live.

Here’s a chart showing the relationship between household-equivalised income and mode shares for people who live in Greater Melbourne:

This chart is similar to the mode share chart for personal income, but there some noticeable differences at the lower incomes – with high private mode share for those on a household equivalised income between $300 and $1000 per week.

Public transport mode shares were highest at the top and bottom of the income spectrum, and lowest for those earning $400-$499 per week.

Similarly, active transport mode share was highest for the bottom and top income bands (probably out of necessity at the bottom end, and from living in walkable and cycling-friendly suburbs at the top end), while private transport mode share showed the inverse pattern, being highest for incomes between $400 and $1000 per week.

The above data was for journeys to work, but what about other travel purposes?

VISTA data shows some similar patterns for the income/age relationships, although the survey sample size doesn’t allow for a split between travel within/outside the City of Melbourne.

PT mode share was highest for those aged 10-29 for all income bands, although the relationship with income is more mixed.

For those in their 40s and 50s, PT mode share was generally higher for those in higher income bands (with the exception of the bottom income band), which may reflect home and work locations.

Younger children had very low public transport mode shares for all income ranges – which is consistent with other findings on this blog about young families.

Here’s an alternative view of the same data with income on the X-axis and a line per age group:

For those aged 30-59 PT mode share generally increased with income (possibly related to higher incomes more likely to work in the city centre), while for those aged 10-29 it generally declined with increasing income. Again, it would appear that age has a much stronger relationship with PT mode share than household income.

Here are overall travel mode shares by income:

It’s a little hard to see, but the mode share pattern is very similar to journeys to work. PT mode shares were higher for the lowest and second highest income bands and lower at middle income bands – with the exception of the highest income band which had much higher private transport mode share.

Socio-economic advantage/disadvantage

Firstly here is the distribution of Greater Melbourne population by age across the 10 deciles for ABS’s index of socio-economic advantage and disadvantage (part of SEIFA). Those deciles are actually for the state of Victoria, and because Melbourne is relatively advantaged compared to regional Victoria, there is a skew to higher deciles. 10 is for the most advantaged areas, and 1 is the most disadvantaged.

Similar to the analysis of income, people in their 40s were more likely to live in more advantaged areas.

Here is a chart of journey to work mode shares by advantage/disadvantage, split between workers aged 20-39 and 40-69:

Somewhat similar to the pattern with income, public transport mode shares were higher for both the most advantaged and most disadvantaged, bottoming out in the third (lowest) decile. This relationship held over younger and older workers, but there was still variance within age bands. When it comes to public transport use, both age and socio-economic advantage/disadvantage were relevant factors, but again it appears that age has a stronger relationship.

As an aside – because it is interesting – here are some charts showing the interaction between socio-economic advantage/disadvantage and other factors for explaining PT mode share, starting with motor vehicle ownership rates (measured at SA1 geography):

There was a relationship between PT mode share and both socio-economic disadvantage/advantage and motor vehicle ownership (except for areas with very high motor vehicle ownership), but motor vehicle ownership appears to have a much larger impact on PT mode share.

The following chart shows home distance from the CBD had a much stronger relationship with PT mode shares than socio-economic advantage/disadvantage:

The density of central city workers also was a much stronger determinant of average public transport mode share than socio-economic advantage/disadvantage:

Occupation

How do PT mode shares vary by occupation? And could variations in the occupation mix across age groups explain variations in PT mode share across age groups?

Firstly, here is the distribution of workers by occupation (using the most aggregated occupation categories defined by ABS), age, and work location (inside v outside City of Melbourne):

There is some variation in occupation distribution across age groups, with 15-19 and 20-29 the most different with many more sales workers and labourers (noting this data excludes people who did not commute to a workplace on census day). Workers aged 30-49 were more likely to be managers or professionals than most other age groups (consistent with income data).

The next chart shows public transport mode shares for journeys to work by occupation and age, disaggregated by other major factors that I have previously found to be significant: parenting status, work location, and immigrant status:

Clerical and administrative workers and professionals generally had the highest PT mode share for all categories. Labourers, machinery operators and (professional) drivers had the lowest PT mode shares, mostly followed by community and personal service workers (many of whom might do shift work – eg aged care, policing, emergency services, hospitality). Managers had significantly lower PT mode shares than professionals – perhaps due to company subsidised cars and/or parking.

You can see a clear relationship between age and public transport mode share in all “panes” of the chart. That is – even when you control for occupation and the other factors – there were still aged-related variations in public transport mode shares. Either some other factor is at work, of age itself is directly a factor influencing mode shares.

Hours worked

Does the amount of hours people worked in a week vary by age, and does it relate to PT mode shares?

Here is the distribution of hours worked by age group:

Workers aged 30-59 were most likely to be working 35+ hours per week, with those older and younger likely to be working fewer hours. So hours worked does not have a linear relationship with age for working-aged adults, and younger adults tend to work less hours.

So what was the relationship between hours worked, age, and PT mode share? Here’s a heat map table of PT mode share by hours worked and age band:

Technical note: you might be wondering why there is a “None” row. That’s for people who worked on census day, but didn’t work any hours in the previous week, for whatever reason.

This chart shows a very clear relationship between PT mode share and age for all ranges of hours worked.

You can also see public transport mode shares were generally highest for people working “full-time” (35-40 hours) and those who didn’t work in the previous week, and were generally lower for people who worked more then 40 hours (possibly working long shifts or multiple jobs – making public transport less convenient?) or less than 35 hours (juggling part-time paid work with other commitments?).

However this didn’t hold for those aged under 30, with full-time teenage workers less likely to use public transport. We’ve already seen that teenage workers generally had lower qualifications, were less likely to work in central Melbourne, less likely to work near a train station, less likely to work somewhere with high job density, less likely to be a recent immigrant, and more likely to work in occupations with lower public transport mode share.

On the bigger question, while PT mode share was generally higher for “full-time” workers, younger adults were less likely to be working full-time. So hours worked actually works against explaining why younger adults were more likely to use public transport.

Studying

Were younger adults more likely to use PT to get to work because they were more likely to also be students?

Certainly younger adults were more likely to be studying, although this dropped to only 10% for those in their 30s:

Here are average journey to work public transport modes shares by age and student-status:

So while workers who were studying certainly had much higher public transport mode shares than those not studying, there was still a strong relationship between age and PT mode share, regardless of whether workers were also students.

Which got me thinking – we’ve learnt that recent immigrants have been predominantly younger adults, and there have been many international students in Melbourne in recent years (at least up until the pandemic). Do these factors inter-play?

Firstly, census data certainly shows that more-recent immigrants were indeed much more likely to be studying, compared to the rest of the population:

In fact, over half of immigrants living in Melbourne who arrived in Australia between the start of 2016 and the census on 9 August 2016 were studying, and more than a third who arrived in the ten years before the census were studying.

So what if we control for how recently someone immigrated to Australia?

Within most arrival year bands, PT mode shares generally declined with age (except for those under 20). So again, these factors do not explain the total variations in public transport mode share by age.

For interest, here are public transport mode shares by student-status and year of arrival into Australia:

Full-time students who also worked were more likely to use public transport to get to work, although they were overtaken by part-time students for those who arrived before 1996. Also, recent immigrants who were not studying were still much more likely to use public transport.

Summary of geographic and demographic factors influencing public transport mode shares

I’ve covered a lot of material over four long posts. So here’s a summary of what I’ve learnt about demographics and public transport mode share in Melbourne in recent pre-pandemic years:

  • Public transport mode share (of all travel) was generally highest for older teenagers, and then fell away with age for those older or younger.
  • Public transport mode share of journeys to work was a little different – peaking for those aged in the mid 20s, and was much lower for teenagers and older adults.
  • Public transport mode share was generally higher in the following circumstances – all of which are generally more common for younger adults (and many of which are closely interrelated). Most of these relationships are quite strong.
    • Geographic factors:
      • living closer to the city centre (strong)
      • living closer to a train station (strong)
      • living in areas with higher residential densities
      • working closer to the city centre (strong)
      • working closer to a train station (strong)
      • working in areas with higher job density (strong)
      • generally travelling to destinations closer to the city centre (strong)
    • Demographic factors:
      • being highly educated
      • having lower rates of motor vehicle ownership (strong)
      • not owning a driver’s licence (strong)
      • not being a parent (strong), particularly a mother
      • being an immigrant, and having more recently immigrated to Australia (strong)
      • being a student (strong)
  • However, these factors don’t seem to fully explain why there are variations in public transport mode share by age (particularly for non-parents). I’ve controlled for several combinations of the stronger factors and still found variations across age bands. There’s likely to be something else about age that influences mode choice.
  • There are other factors (all demographic) that have a relationship with public transport mode shares, but these factors did not peak for young adults, unlike public transport mode share. So they actually work against explaining higher public transport use by younger adults. These saw higher public transport mode shares being associated with:
    • both very low and high incomes (but not the highest incomes)
    • both highly socio-economically advantaged areas and highly socio-economically disadvantaged areas
    • working full-time (35-40 hours per week)
    • having a professional or administrative/clerical occupation
    • not being a labourer, machinery operator, or professional driver
  • Women were more likely than men to use public transport to get to work for most age ranges (except ages 38-48), and this seems to be at least partly related to their higher levels of education, which in turn probably explains why they are more likely to work in the city centre.

For more about factors associated with higher public transport use, see What explains variations in journey to work mode shares between and within Australian cities?

How are these factors changing over time?

Elsewhere on this blog I’ve uncovered other likely explanations for increased public transport mode share, including things such as increasing population density and employment density – see What might explain journey to work mode shifts in Australia’s largest cities? (2006-2016). However that analysis didn’t look at changes in the geography and demographics of people of different ages.

In this series I’ve confirmed some “demographic” factors that are related to public transport use that have also changed in favour of public transport use over those pre-pandemic years:

But there have been other demographic shifts that probably worked against increasing public transport mode share over the pre-pandemic years:

  • The proportion of the working population who were parents rose from 22.6% to 27.1% for those working in the City of Melbourne, and from 25.3% to 27.3% for the rest of Greater Melbourne (2006 to 2016). As an aside: there was the little change in the average age of working parents – for women it went from 38.6 years in 2006 to 39.6 years in 2016 and for men it went from 40.0 to 40.3 years.
  • The proportion of people working in the City of Melbourne who were under 40 years of age declined slightly from 58.3% to 57.2% (2006 to 2016).
  • Motor vehicle ownership rates have risen significantly for adults over 60. Or put another way, for people born before around 1950, there was almost no change in their rates of motor vehicle ownership between 2011 and 2016, despite them aging 5 years. See: How has motor vehicle ownership changed in Australian cities for different age groups?

In a future post I might look at whether there has been a shift in where younger adults live and work geographically (eg proximity to the CBD, proximity to train stations, residential densities). This would be particularly interesting for the “post-pandemic” world, however it will probably need to wait for 2026 census data.

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Posted by chrisloader

How has motor vehicle ownership changed in Australian cities for different age groups?

Sun 18 July, 2021

Motor vehicle ownership has a strong relationship with private transport mode share, and has recently seen declines in some Australian cities (e.g. Melbourne). In addition, we know that younger adults more recently have been deferring the acquisition of a driver’s licence (see: Update on Australian transport trends (December 2020)), so have they also been deferring motor vehicle ownership? For which age ranges has motor vehicle ownership increased and decreased? How might this have influenced journey to work mode shares? And how do changes in motor vehicle ownership relate to changes in driver’s licence ownership?

This post aims to answer those questions for Australia’s six largest cities, primarily using 2011 and 2016 census data, but also using household travel survey data for Melbourne.

But first…

A quick update on motor vehicle ownership trends in Australia

As I was writing this post, ABS released data for their Census of Motor Vehicle use – January 2021 (sadly the last motor vehicle census run by the ABS). I’ve matched this up with the latest available population data, and found a small but significant uptick in motor vehicle ownership rates in all Australian states in 2021 following the onset of the COVID-19 pandemic:

Image

I suspect this uptick will be at least partly due to a massive reduction in immigrants into Australia – who I’ve recently found to have much lower rates of motor vehicle ownership for the first few years they live in Australia (see Why were recent immigrants to Melbourne more likely to use public transport to get to work?) and also probably low motor vehicle ownership – see How and why does driver’s licence ownership vary across Sydney?).

It could also reflect a mode shift from public to private transport, as people seek to avoid the perceived risk of COVID-19 infection on public transport.

But there’s another likely explanation of this uptick and it relates to ages, so keep reading.

What does household travel survey data tell us about motor vehicle ownership by age in Melbourne?

My preferred measure is the ratio of household motor vehicles to adults of driving age (notionally 18 to 84).

Using Melbourne household travel survey data (VISTA), I can calculate the average ratio by age group pretty easily, and the following chart also breaks this down for parents, children, and other people (living in households without parent-children relationships):

With 2-year age bands there is a limited span of age ranges for some categories due to the small survey sample sizes (I’m only showing data points with 400+ people). So here is a similar chart using 4-year age bands, which washes out some detail but provides values for wider age ranges:

You can see some pretty clear patterns. Motor vehicle ownership was high for households with children (peaking for ages 12-13), parents – particularly in their late 40s, and those aged in their 50s and early 60s in households without children. Average motor vehicle ownership was lowest for young adults living away from their parents, and for those in older age groups.

Unfortunately the VISTA dataset isn’t really big enough to enable significant analysis of changes over time – the sample sizes for age bands get too thin when you split the data over years or even groups of years. I’d like to understand changes over time, so…

What can census data tell us about motor vehicle ownership by age?

Unfortunately it’s not possible to calculate the ratio of household motor vehicles to adults using Census (of Housing and Population) data (at least when using ABS Census TableBuilder).

The numerator is pretty easy for the 2011 and 2016 censuses which classify private dwellings as having zero, 1, 2, 3, 4, …, 28, 29, or “30 or more” motor vehicles. Only a very small number of households report 30+ motor vehicles. Unfortunately the 2006 census’s top reporting category is “4 or more” motor vehicles which means you cannot calculate the motor vehicle ratio for many households.

My preferred denominator – the number of adults of driving age – is not available in ABS’s Census TableBuilder. The closest I can get is the “number of persons usually resident” for dwellings – and private dwelling are classified as having 1, 2, 3, 4, 4, 5, 6, 7, or “8 or more” usual residents in the 2006, 2011 and 20216 censuses. Obviously I cannot calculate the ratio of motor vehicles to usual residents if there were “8 or more” usual residents.

(For the census data nerds out there: I tried to get a good guess of adults by using family composition, but it can only distinguish parents (who may or may not be of driving age), children under 15, and dependent students aged 15-24. And worse still, that doesn’t work for multi-family households, and you cannot filter for single family households as well as distinguish family types.)

So I’m stuck with household motor vehicles per person usually resident. And an obvious drawback is that motor vehicle ownership will be lower for adults living in households with children, compared to those without children.

Here’s the distribution of motor vehicle : household size ratios for Greater Melbourne for 2011 and 2016 (I’ve left out 2006 because too many households cannot be calculated). There are a lot of different ratio values, but only about a dozen common ratios, several of which I have labelled on the chart.

Sure enough, there were much lower ownership ratios for children’s households, and adult ages where children were more likely to be resident (generally mid-20s to around 60). Higher ratios peaked for people in their early 60s and then steadily declined into older ages, with most people in their 90s living in dwellings with no motor vehicles (if they are not living in non-private dwellings). For adults in their 60s, one car per person was the most common ratio.

I can also calculate the average motor vehicle ownership ratio for each age as an aggregate statistic (excluding 3-4% of households where I don’t know the precise number of residents and motor vehicles). Here’s how that looks for 2011 and 2016:

As mentioned, I cannot calculate this ratio for households where I don’t know the precise number of both motor vehicles and usual residents (or where I don’t know the number of usual residents, but do know there were zero motor vehicles). Across Australia’s five biggest cities that’s 4.1% of population in the 2016 census, 3.4% in 2011, and 10.4% in 2006 (but much higher proportions of younger adults). They sound like small numbers, but aren’t that small when you consider the shifts in ownership between censuses.

But there is another way to classify households with fewer unknowns – whether they have:

  • no motor vehicles;
  • fewer usual residents than motor vehicles; or
  • at least one motor vehicle per usual resident.

The benefit of this approach is that you can classify almost half of the households where you cannot calculate an exact ratio:

  • If a household had 30+ motor vehicles (very rare) but fewer than 8 usual residents, then it had at least one vehicle per person.
  • If a household had 4+ motor vehicles (quite common in 2006 census) and 4 or fewer usual residents, then it had at least one vehicle per person.
  • If a household had 8+ usual residents (about 1.3% of population in 2016), but 7 or fewer motor vehicles (93.5% of the 1.3%), then it had less than one vehicle per person.

Across Australia’s biggest five cities I can now classify all but 2.5% of the 2016 population, 2.3% of the 2011 population and 6.1% of the 2006 population.

The next chart shows the distribution of this categorisation for Melbourne (using Melbourne Statistic Division for 2006, and “Greater Melbourne” for 2011 and 2016). I’ve put the remaining people living in uncategorisable households (“unknown”) in between 0 and <1 motor vehicles per person, as it is likely households who did not answer the question about household motor vehicles probably had few or no motor vehicles (refer to the appendix at the end of this post for more discussion).

I have also removed people who did not provide an answer to the usual residents question (hoping they are not overly biased – they are probably households who didn’t respond to the census), and non-private dwellings (where motor vehicle ownership is not recorded).

The patterns are similar to the previous chart, with a double hump pattern of 1+ motor vehicles per person. There are some changes over time, which I’ll discuss shortly.

Unfortunately the unknown band is still pretty wide in 2006 – in fact I still cannot categorise around 15% of 20 year olds in 2006 (many must have lived in households with 4+ motor vehicles), so it doesn’t really support good time series evaluation between 2006 and 2011.

So how has motor vehicle ownership by age changed over time in Melbourne?

Many of the previous charts were animated over 2-3 censuses but there’s a lot of take in with different lines moving in different directions for different age groups. To help to get better sense of those changes, what follows are a set a static charts, and then some discussion summarising the patterns.

Firstly, the change in average motor vehicles per usual resident for each age year (but only for households where the exact number of motor vehicles and usual residents is known):

Secondly, here’s a static chart that shows the proportion of population living in households known to have 1+ motor vehicles per person for both 2011 and 2016 for Melbourne, and the difference between 2011 and 2016 (I’ve excluded 2006 as there were too more unknowns). I haven’t removed uncategorisable households from the calculations, on the assumption they bias towards lower motor vehicle ownership (as discussed above).

This chart shows very little change for children under 18, but also very few such households had 1+ motor vehicle per occupant in 2011 or 2016 so it’s not a very useful metric. Lower ownership ratios are much more common for households with children, so here’s a chart showing the proportion of the population living in dwellings with at least 0.5 motor vehicles per person, and the change between 2011 and 2016: (I used equivalent rules to classify households with 8+ usual residents or 30+ motor vehicles, where possible)

And finally, here’s a chart showing the proportion of the population living in dwellings reported to have no motor vehicles (probably an underestimate as I think many “not stated” responses are likely to be zero motor vehicles).

Each of these charts paints a similar picture. Here’s a summary by age ranges:

Age rangeMotor vehicle ownership trend
0-17Slight increase
18-26Certainly a decline, including around 1-2% more people living in dwellings with no motor vehicles.
27-45Small decline of around 2-3% living in households with 1+ or 0.5+ motor vehicles per person. But there was no significant increase in households with no motor vehicles, and average motor vehicles per person was relatively stable.
46-64Very small decline (around 1%) of people living in households with 1+ and 0.5+ motor vehicles per person, but little change in households without motor vehicles.
65+Significant increase in metrics of motor vehicle ownership, and a significant decline in dwellings without any motor vehicles.

So while overall motor vehicle ownership in Melbourne declined between 2011 and 2016, it was mostly in working aged adults, partly offset by family households and older adults increasing their rates of motor vehicle ownership.

And going back to the uptick in motor vehicle ownership in January 2021… recent immigrants to Australia have skewed towards young adults (particularly through skilled migrant visas). The massive reductions in immigrants in 2021 will mean the population contains proportionately fewer young adults – who generally have low car ownership, particularly recent immigrants. This slightly but significantly smaller number of young adults will no longer be fully offsetting those over 70 who are increasingly retaining motor vehicles longer into their life.

What about other Australian cities?

As above, I’ll present a series of charts showing the various metrics then summarise the trends.

Firstly, a chart showing the average ratio of motor vehicles per resident by age for all cities between 2011 and 2016 – for private dwellings where the exact number of vehicles and usual occupants is known:

To help see those changes, here is a static chart showing the change in average motor vehicles per person by age (I’ve used three-year age bands as the data otherwise gets a bit too noisy):

Here’s an animated chart showing the percentage of people living in private dwellings with 1+ motor vehicle per person:

There’s a lot going on in that animation (and the data gets a bit noisy for Canberra due to the relatively small population), so next is a chart showing the difference in population living with 1+ motor vehicles per usual resident:

As before, the threshold of 1 motor vehicle per person is not useful for examining the households of children, so here’s a similar change chart for the 0.5 motor vehicles per person threshold:

These difference charts mostly form duck-shaped curves with a slight increases for children, a mixture of increases and decreases for working aged adults, and a large increase for older adults (particularly for those in their 70s).

For young adults (18-30), motor vehicle ownership mostly declined in Melbourne and Canberra, but for Perth and Adelaide there was a large increase in ownership for those aged 21-39.

There was less change in ownership for those aged 40-54. On the metrics of proportion of population with 1+ and 0.5+ motor vehicles per resident there was a small decline in all cities, but for average motor vehicles per person, some cities declined and some increased. So perhaps the amount of variation in motor vehicle ownership narrowed in this age range.

Melbourne was mostly at the bottom of the pack, with Brisbane, Adelaide or Perth mostly on top.

To continue this analysis, I want to know whether these changes in motor vehicle ownership might be impacted mode share, but first we need to look at…

How did journey to work mode shares change by age?

Here are public transport mode shares of journeys to work by age for Australia’s six biggest cities, 2006 to 2016:

Public transport mode shares were much higher for younger adults in all cities in all censuses. Most cities rose between 2006 and 2011, but then different cities went in different directions between 2011 and 2016.

Here’s the mode shift between 2006 and 2011:

Most cities and ages had a mode shift towards public transport, particularly for those aged around 30, but less so for young adults.

Here’s the mode shift between 2011 and 2016:

Between 2011 and 2016 there was a mode shift to public transport in most cities for people in their 30s and 40s, but for younger adults there was a decline in public transport mode share in most cities, with only Sydney, Melbourne, and Canberra seeing growth.

However we are talking about motor vehicle ownership, and declining motor vehicle ownership may be because of mode shifts to walking, cycling, and/or public transport. So it is worth also looking at private transport mode shares (journeys involving private motorised modes but not public transport modes).

To help see the differences, here is the mode shift for private transport 2006 to 2011:

There’s a similar curve for all cities, but different cities are higher or lower on the chart. There was a shift towards private transport for young workers, a shift away in most cities for those in their 20s and 30s, and smaller shifts for those in their 40s and 50s

And from 2011 to 2016:

Again similar curves across the cities, with younger adults again more likely to shift towards private transport in most cities, a big shift away from private transport for those in their 30s and early 40s in Sydney and Melbourne, and smaller shifts for those in their 50s and 60s.

What’s really interesting here is that the mode share and mode shift curves are similar shapes across most cities (except the much smaller city of Canberra). There are some age-related patterns of travel behaviour change consistent across Australia’s five biggest cities.

How did changes in motor vehicle ownership compare to changes in private transport mode share?

If motor vehicle ownership increases you might expect an increase in private transport mode shares, and likewise you might expect a decrease in ownership to relate to a decline in private transport mode shares.

Indeed when you look at cities as a whole, there is generally a strong relationship between these measures, although different cities moved in different directions between 2011 and 2016.

In this post I’m interested in shifts for people in different age groups. The following chart shows the changes in motor vehicle ownership and private transport mode shares for each city and age group: (note different axis scales are used in each row of charts)

However I’m particularly interested in the change in these factors, rather than where they landed in each of 2011 and 2016. So the following chart plots the change in motor vehicles per 100 persons and the change in private transport mode share of journeys to work between 2011 and 2016 for five-year age bands (noting that of course every living person got five years older between the censuses).

That’s a busy chart but let me take you though it.

There’s one mostly empty quadrant on this chart (top-left): for no city / age band combinations did motor vehicle ownership decline but private transport mode share increase, which isn’t really surprising.

But in city / age band combinations where motor vehicle ownership did increase there there wasn’t always an increase in private transport mode shares – quite often there was actually a decline. So increasing motor vehicle ownership doesn’t necessarily translate into higher private transport mode shares – for journeys to work at least. Perhaps increasing affordability of motor vehicles means more people own them, but don’t necessarily switch to using them to get to work.

The largest declines in private transport mode share occurred in city/age band combinations that actually saw a slight increase in motor vehicle ownership.

The cloud is quite spread out – which to me suggests that motor vehicle ownership is probably not a major explanation for changes in mode share between 2011 and 2016 – there must be many other factors at play to explain changes in mode shares across cities. Indeed, see my post What might explain journey to work mode shifts in Australia’s largest cities? (2006-2016) for more discussion on these likely factors.

What is the relationship between motor vehicle ownership and driver’s licence ownership?

As I’ve previously covered on this blog (eg see: Update on Australian transport trends (December 2020)), data is available on the number of licenced drivers by different age groups, but only at the state level.

I’d prefer not to be using state level data as city and country areas might wash each other out, but I’d don’t have a lot of choice because of data availability. (Licencing data is available at postcode resolution in New South Wales (see How and why does driver’s licence ownership vary across Sydney?), but unfortunately you cannot disaggregate by both geography and age.)

Here’s another (busy) chart showing the relationship between licence and motor vehicle ownership by age band and city, across 2011 and 2016:

The main thing to take away here is that most of the points are within a diagonal cloud from bottom-left to top-right – as you might expect: there is less value having a driver’s licence if you don’t own a car, and little point owning a car if you don’t have a licence to drive it. The exceptions to the diagonal cloud are mostly age bands 30-39 and 40-49, where the average motor vehicle ownership rates are lower because many of these people often have children in their households, and I cannot remove children from the calculation using census data.

But I can control for the issue of children by going back to city geography by using household travel survey data for Melbourne (VISTA, 2012-2018). The following chart shows the relationship between average motor vehicle and driver’s licence ownership for adults by different age brackets.

The data points again generally form a diagonal cloud as you’d expect. Higher motor vehicle ownership generally correlates with higher licence ownership.

The change in ownership rates by age are interesting. Children under 10, on average, lived in households where adults have very high levels of motor vehicle and licence ownership. Licence ownership was slightly lower for adults in households with children aged 10-17 (although this could just be “noise” from the survey sample). Young adults (18-22) then on average lived in households with relatively low motor vehicle and licence ownership. As you move into older age brackets licence ownership increased, followed by increases in motor vehicle ownership, with both peaking again around ages 40-69 (although not as high as households with children). Those aged 70-79 and 80+ then had significantly lower rates of licence and vehicle ownership, as you might expect as people age and become less able to drive. These patterns are fairly consistent with the census data scatter plot, except for the key parenting age bands of 30-39 and 40-49 where the census data analysis cannot calculate ownership per adult (just per person).

How has licence and motor vehicle ownership been changing for different age groups?

Across Australia, licence ownership has been increasing in recent years for older adults (particularly those over 70), and declining in those aged under 30 in states such as Victoria, New South Wales and Tasmania (for more detail see Update on Australian transport trends (December 2020)).

The following chart shows state-level changes in motor vehicle ownership and licence ownership between 2011 and 2016 by age bands: (note different scales on each axis)

This chart also shows something of a direct relationship between changes in motor vehicle and licence ownership, with people aged 70+ having the largest increases in both measures (except for Victorians aged 80+ who saw a decline in licence ownership). Younger age bands often had a decline in licence ownership, even if motor vehicle ownership in their households increased slightly (on average). For those aged in their 40s, there was generally an increase in licence ownership but only small changes in motor vehicle ownership – including slight declines in most states.

Teenagers in the ACT were an outlier, where there was a significant decline in licence ownership between 2011 and 2016 that someone with local knowledge might be able to explain.

Overall the relationship between changes licence ownership and changes in motor vehicle ownership is not super strong. Increasing licence ownership does not automatically translate into increasing motor vehicle ownership. There must be more factors at play.

I hope you’ve found this post interesting.

Appendix: What about households where census data is missing?

The non-response rate to the question about household motor vehicles was around 8.4% in 2016 (up from 6.5% in 2011) and most of these were for people who did not respond to the census at all. Non-response was fairly consistent across age groups as the next chart shows. Quite a few people had a response to the question about number of usual occupants, but did not respond to the question about motor vehicles. Poking around census data, these people often:

  • didn’t answer other questions;
  • were less likely to be in the labour force;
  • were generally on lower incomes;
  • were more likely to be renting;
  • were less likely to have a mortgage; and
  • were more likely to live in a flat, apartment or unit, and less likely to live in a standalone/separate house.

So my guess is that they were less likely to have high motor vehicle ownership.

The number of “not applicable” responses increased significantly into older age groups, and I expect most of these will be people in non-private dwellings (e.g. aged care). I have removed people with “not applicable” responses for usual occupants and household motor vehicles as they are likely to be non-private dwellings.

The chart gets a bit noisy for ages above 100 as very few such people live in private dwellings.

2 Comments | Australian Cities, Brisbane, Car ownership, drivers license, Melbourne, Mode share, Mode shift, Sydney | Tagged: , | Permalink
Posted by chrisloader

Why are young adults more likely to use public transport? (an exploration of mode shares by age – part 3)

Wed 18 November, 2020

I’ve been exploring data to explain why younger adults are more likely to use public transport (PT) than older adults in Melbourne. This third post in a series looks at the relationship between public transport mode share and parenthood, the year in which people were born, whether people were born in Australia or overseas, and how recently immigrants arrived in Australia.

I’m using VISTA household travel survey data (all travel) and ABS Census data (journey to work only). For more detail about the data, see the first post in the series.

Parenthood

Are younger adults more likely to use public transport because they don’t (yet) have dependent children?

Consistent with previous analysis on this blog, there is a relationship between PT mode share and whether people are parents within family households. Here’s the data for general travel from VISTA 2012-18:

Parents were much less likely to use public transport than non-parents of the same age, with mums between 35 and 55 having a lower mode share (on average) than dads in the same age range.

The census tells us whether a worker did unpaid child care for a child of their own in the two weeks prior to the census, which I am using to distinguish parents and non-parents.

The following chart shows the proportion of working men and women who were parents, animated over censuses 2006 to 2016.

Parenting peaked around age 40 for male and female workers, and the proportion of workers who were parenting went up between 2006 and 2016.

So how do public transport mode shares vary by age if we separate out parents and non-parents? The following chart answers this, and also separates workers by whether or not they worked in the City of Melbourne local government area (a known major factor influencing mode shares), animating results over 2006, 2011, and 2016:

Note there is a different Y-axis scale for City of Melbourne and elsewhere.

There are a few really interesting take-aways here:

  • Parenting workers mostly had lower public transport mode shares than non-parenting workers of the same age, except for:
    • dads over 30 who worked in the City of Melbourne,
    • mums in their early 30s who worked in the City of Melbourne in 2016, and
    • mums and dads in their 50s who worked outside the City of Melbourne (who had low PT mode shares around 4-5%, similar to non-parenting workers of the same age)
  • Public transport mode shares increased over time for almost all age bands, work locations, and for parenting and non-parenting workers.
  • Public transport mode shares for journeys to work in the City of Melbourne mostly declined with increasing age between 20 and 50, regardless of parenting responsibilities. Other age-related factors must be at play.
  • For people who worked outside the City of Melbourne, the mode share profile across age changed significantly over time for young adults. In 2006 there was a steady decline with age, but in 2011 PT mode shares were generally flat for those in their 20s, and in 2016 PT mode shares peaked for women in their late 20s (and also had a quite new pattern for dads in their 20s).
  • For parenting workers who work outside the City of Melbourne there was actually a slightly higher PT mode share for those over the age of 50. Parents over 50 might have older children who are more independent and therefore less reliant on their parents for transport. This might make it easier for the parents to use public transport. However this trend did not hold for dads in 2016.
  • PT mode shares for non-parenting women increased slightly beyond age 55 for all work locations. This will include women who were never parents, as well mums with non-dependent children so might again reflect a small return to public transport once children become independent. It may also be influenced by discounted PT “Seniors” fares available to people over 60 who are not working 35+ hours per week.

Lower public transport mode shares for parents is not surprising – they may be more time-poor and need more transport flexibility to link trips – eg dropping kids at childcare on the way to work can be more difficult with public transport (although it doesn’t seem to impact men travelling to the city centre nearly as much as women – I suspect because women are more likely to be working part time and doing childcare drop-offs and pick-ups). Parents may decide that time saving and convenience moving children is more important to them than lower transport costs from using PT.

However, addition of parenting responsibilities does not fully explain why public transport mode share generally declined with increasing age, particularly for non-parenting workers.

But I’m curious about the changing profile of mode share by age over time. Could it be influenced by…

Birth year / generations

Does public transport mode share vary by age and/or does it vary by when people were born, with different mode choices by different generations? To answer this I’m going to look at mode shares by both age and birth year.

For this analysis, I want to compare mode shares of birth year cohorts over time. The exact composition of these cohorts will change over time as there are deaths, new immigrants, and people who move overseas. I can only easily control for immigrants using census data – so for this section of my analysis I’m going to remove people not born in Australia (I will return to look at mode shares of immigrants shortly). Of course some people born in Australia who worked in Melbourne in 2016 may have spent a significant time living outside Australia before a census so this isn’t perfect.

Firstly, here’s a chart of journey to work PT mode shares by age, work location, and parenting status across 2006, 2011, and 2016 for people born in Australia:

Technical note: I’ve excluded data points where there was a small number of commuters, or a small number of public transport journeys where calculations are impacted by ABS randomisation to protect privacy.

You can see the general shape of the census year curves are similar within each quadrant (with a little noise at the extremes of age probably due to smaller volumes), suggesting a similar relationship between PT mode share and age holds over time.

We can clearly see how mode shares have increased over time for age bands, including:

  • those who work in the City of Melbourne (top row),
  • non-parenting younger adults who worked outside the City of Melbourne (bottom-left), and
  • to a smaller extent parents in their 30s and 40s who worked outside the City of Melbourne (bottom-right).

There were PT mode share spikes at age band 16-17 (at least for people working outside the City of Melbourne), which is just before people can gain independent licences. Those aged 18-19 working outside the City of Melbourne had a much lower PT mode share than those aged 16-17, and PT mode shares were lower again for those aged 15 who are perhaps more likely to work locally or be driven to work by parents.

So is this a general mode shift over time, or is it something intrinsic to birth years or “generations”? The next chart is similar to the previous, but the X-axis is notional birth year (approximated by census year – age at census time, which will be within a year of actual birth years).

Technical notes: For this chart I’ve calculated the 2 year birth year bands so that the youngest birth band is for ages 15-16 in all census years.

Let’s walk through the quadrants:

  • Non-parenting, City of Melbourne (top-left): PT mode shares have increased over time for those born between the 1940s and mid-1980s, despite these commuters getting older (assuming the same people still work within the City of Melbourne). This suggests general mode shift to PT over time has been stronger than any mode shift away from PT due to aging.
  • Parenting, City of Melbourne (top-right): PT mode shares have increased over time for almost all birth years, despite getting older (although the membership of this cohort will change as people acquire and lose parenting responsibilities). This is the same as non-parenting workers in the City of Melbourne.
  • Non-parenting, outside City of Melbourne (bottom-left): Ignoring those aged 15-22, mode shifts are generally smaller and not all in the same direction. If there was a negative relationships between age and PT mode share, you’d expect to see a shift away from PT between 2006 and 2016 for all cohorts. But for those born between around 1975 and 1985 (younger generation X and older millennials) and those born between 1940 and 1958 (mostly Baby Boomers) there was a small shift towards PT over time, despite them getting older. However these mode shifts were in the order of only 1-2%. Those born between 1960 and 1974 (mostly Gen X) shifted away from PT over time.
  • Parenting, outside City of Melbourne (bottom-right): For people born between around 1955 and 1980 (baby boomers and gen X) there was a shift towards PT between census years 2011 and 2016, despite people ageing. However in this quadrant mode shares were pretty flat and low over most ages (except at the young and old extremes of the cohort).

Of course many people will move from the left column to the right column as they start families, and then perhaps back to left column when they have adult children who no longer need care, so this analysis isn’t perfect.

So are there generational effects on PT mode share? Between 2006 and 2016 there was a significant shift towards PT in Melbourne for most birth years, parenting statuses and work locations, with only non-parenting workers born between 1960 and 1974 and working outside the City of Melbourne shifting away from PT. So the answer is no – any impact from birth year appears to be very small, and was generally swamped by an overall mode shift towards public transport.

That analysis was for for people born in Australia, but what about immigrants?

Immigrants to Australia

Are people who immigrated into Australia more recently, more likely to use PT to get to work? The next chart provides a clear “yes” answer to that question. I’ve included parenting status and work location as known significant factors, and animated the chart over censuses 2006, 2011 and 2016.

While the lines appear to shift left, they are really shifting up or down (people’s birth year doesn’t change), and are growing on the left with new younger workers entering the labour market, and falling away on the right as people leave the workforce.

Time of immigration had a big impact on PT mode shares – with people who arrived in Australia in the five years before a census most likely to use PT to get to work. The biggest difference in PT mode shares was for recent non-parenting immigrants working outside the City of Melbourne (bottom-left quadrant). Perhaps if public transport quality was boosted in areas with many recent immigrants there might be less loss of mode share over time. Or the drop in mode share might reflect people moving to areas with lower quality public transport.

For those working outside the City of Melbourne, PT mode share quickly fell after arrival into Australia, and after around 20 years living in Australia immigrant’s mode shares are similar to those who have been in Australia longer (or were born in Australia).

The chart also shows that there are age-related factors at play (beyond parenting and work location), regardless of whether people were born in Australia or immigrated – although much less so if they are parenting.

So could it be that recent immigrants make up a greater share of young adults, and might this explain the overall average mode shares across age groups?

The next chart shows the distribution of working population in five-year age bands by year of immigration / those born in Australia. I’ve animated this over 2006 to 2016. While the chart appears to animate with vertical movements, people actually shift one column to the right between census years.

If you watch the chart you’ll see that the immigrant share of the working population under 45 years increased between 2006 and 2016, with strong surges in immigration after 2006. This will undoubtedly impact the overall mode share for younger adults, but it doesn’t explain all of the mode share variance by age. The previous chart showed age-related factors influencing PT mode shares, regardless of when people moved to Australia.

I will explore potential reasons why recent immigrants were more likely to use public transport to get to work in an upcoming post.

Can we now explain why young adults are more likely to use public transport?

So far we’ve established that the following factors appear to have a strong impact on public transport mode shares:

  • Workplace distance from the CBD
  • Recency of immigration to Australia
  • Parenting status
  • Age

If the first three of these factors are the most important, and age or other age-related factors were not important, then we would expect flat mode shares across ages when you control for the other three factors.

The following matrix-of-worms chart combines all four factors. But please note that the Y axis within each row has a different scale and doesn’t necessarily start at zero. I am really looking at the slope of the line within each matrix cell, so I’m not too concerned about the actual values. I’ve only shown data points that included at least 400 commuters, and I’ve removed some columns and rows where data was too sparse to show meaningful trends.

How to make sense of this chart? Well, if the factors of parenting, arrival year and work distance from the CBD explained all the differences between age groups, then you would expect these lines to be flat within each matrix cell.

On the parenting (right) side of the chart, many of the worm lines are indeed quite flat, with the exception of those who arrived between 2006 and 2015 and those who worked within 2 km of the Melbourne CBD. Even though many of these matrix cells only have two or three data points, most data points include thousands of commuters so I don’t expect much false “noise” in the chart.

Within non-parenting commuters:

  • There is generally either a relationship with age, or a very low and flat PT mode share across ages, suggesting age itself, or some other age-related factors were at play.
  • The relationship with age appears to be strongest for more recent immigrants. The Born in Australia column also shows a strong relationship with age but this also has the widest age range. The columns for those who arrived between 1976 and 1995 only contain 3 to 5 age bands (all 30+), which will partly explain why there is less of an evident slope in the line.
  • Age band 60-69 is often an outlier to the trend, particularly for those born in Australia or who arrived between 1976 and 1985, again perhaps related to discounted “Seniors” public transport fares.

So I haven’t been able to fully explain variations in PT use by age. Age itself may be a factor, there may be other age-relevant factors that are important, or more likely there are lots of complex interactions between factors that are hard to unpick.

The next post in this series will look at the impact of income, socio-economic advantage/disadvantage, and occupation on PT mode shares across ages.

Leave a Comment » | Melbourne, Migration, Mode share | Tagged: , | Permalink
Posted by chrisloader

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