[Last updated 28 May 2020]
Roads in Victoria have been noticeably quieter during the pandemic, but just how much has traffic reduced? Has it varied by day of the week, time of day, and/or distance from the city centre? How have volumes increased as restrictions have been eased?
To answer these questions I’ve downloaded traffic signal loop vehicle count data from data.vic.gov.au. The data includes vehicle detection loops at 3,760 signalised intersections across Victoria (87% of which are in Greater Melbourne).
I should state that it is not a perfect measure of traffic volume:
- It may under-count motorway-based and rural travel which may cross fewer loop detectors.
- There are occasional faults with loops, and I’m only able to filter out some of the faulty data (supplied with negative count values), so there is a little noise but I will attempt to wash that out by using median counts rather than sums or averages (although charts of averages show very similar patterns to charts of medians).
- Some vehicles moving through an intersection might get counted at multiple loops, but I would hope this has minimal impact on overall traffic volume trends.
How have traffic volumes reduced during the pandemic?
Firstly, median 24-hour loop volumes for each day:
Note: the actual numbers aren’t very meaningful, it is the relative numbers that matter. Unfortunately at the time of updating, data for some dates was missing (or clearly erroneous so I have excluded it).
Traffic volumes declined over the second half of March 2020, as more restrictions were introduced, students stopped attending schools and universities, and workers were asked to work from home if possible.
School holidays started early (on Tuesday 24 March) although many students stayed home in the last days of term. School resumed on Wednesday 15 April with most students remote learning at home.
The first official easing of restrictions took effect from Wednesday 13 May (week 20) allowing some social gatherings and this has seen some significant traffic growth (although it appears traffic volumes were already slowly increasing before that date).
There are variances by day type and by week, so here is a chart looking changes by day of the week, relative to the first two weeks of March 2020:
At their lowest, weekday volumes went down around 40%, while weekend volumes went down more like 50%.
In late-May volumes were down more like 20-25%, with significant growth on weekends.
A curious outlier is Thursday in the week of 5 April – this was Thursday before Good Friday, so there may have been some travel to holiday homes, or other travel that happens normally on a Friday being the end of the working week.
However we should be careful because there is some underlying seasonality in traffic volumes, as well as week-to-week variations (perhaps impacted by events and/or weather). Here is a chart comparing 2020 with 2019 for weekdays, Saturdays and Sundays (excluding public holidays):
You can see again weekends recovering the fastest so far.
The next chart compares each 2020 week with the same week 2019, although it is important to note that there was quite a bit of week to week variation in 2019:
On this measure, weekdays were down around 38% on 2019, but have recovered to be ~27% down in week 20. Weekends were down around 50%, but Saturday 16 May was only ~22% down on the equivalent Saturday in 2019. Sundays had recovered to be only ~37% down on 2019 in week 19.
How has traffic reduced by time of day?
The traffic signal data is presented in 15 minute intervals, generating huge amounts of detailed data (more than I could load into Tableau Public which has a limit of 15 million records). I’ve managed to load data for most days of the week for March and April 2020.
Here’s a look at the traffic volumes by time of day for Wednesdays:
You can see a significant flattening of the traditional peaks from late March, although curiously the PM peak still commences around 3 pm, even during the school holidays.
Evening traffic was down considerably but it’s a little hard to gauge this reduction the chart. So here is a chart showing traffic volume changes relative to the first week of March:
Volumes were down the most in the evenings (particularly around 9 pm) which might reflect the closure of hospitality venues, cessation of sports and reduced social activity. The AM and PM peak periods are down around 50%, while the inter-peak period has held up the most – being only down around 30%.
I should point out that this analysis compares to a baseline of a single day, and there may be some associated noise (eg weather or event impacts on particular days).
Here is the same for Fridays:
10 April was Good Friday, hence much quieter traffic with retail trading restrictions.
Late evening traffic is down even more than for Wednesdays, which probably reflects higher volumes of hospitality-related travel on Friday nights.
Here is Saturdays:
The Saturday profile shape hasn’t changed as much as weekdays, but the evenings are down most significantly.
25 April was the Anzac Day public holiday, and the spike in afternoon travel probably reflects retail trading restrictions that apply until 1pm.
Curiously there are several spikes in the curve in the morning – and they are the 15 minute intervals leading up to the hours of 7am, 8am, 9am, and 10am. Initially I wondered if it was a data quality issue, but perhaps they reflect a surge in travel just in time for work shifts and other activities that start on the hour.
For some reason traffic volumes were relatively low around 6 am on Saturday 7 March, which has resulted in other days showing less reduction.
Saturday night travel is down considerably – by over 70% by midnight. You can also see early Saturday morning (Friday night) travel down around 60-70%.
Here is Sundays:
Sunday 12 April was Easter Sunday, which might explain quieter traffic. Sunday 8 March was on the Labour Day long weekend (including the Moomba festival), which probably explains the much busier traffic that Sunday night (not being a “school night”). You can more clearly see that on the following chart:
One aside on this – it’s possible to compare the traffic profiles of different days of the week (sorry I had to exclude Tuesdays and Thursdays due to data volumes). Here’s the first week of March before the shutdown:
This data suggests a roughly a one hour lag on Sunday mornings compared to Saturday mornings – ie travel volumes hold up an hour later on Saturday nights and ramp up an hour later on Sunday mornings. This pattern holds up for other weeks.
Here’s another look at relative time of day traffic volumes for March and most of April:
If you look closely (no, your eyes are not losing focus!) you can see:
- Significant reductions after schools finished on 23 March
- A surge in traffic on 9 April – the Thursday before Good Friday
- Extremely quiet traffic on Good Friday (10 April)
- Generally higher traffic on the last weekday of the week, particularly in the afternoon and evening (including during the shut down period)
- The middle of the day being busier on (pre-shutdown) Saturdays compared to weekdays.
Have traffic impacts been different by distance from the CBD?
Here’s a chart showing year-on-year reduction in median traffic volumes at intersections by distance from the Melbourne CBD for weeks 14 and 15 (the lowest two weeks of the lock-down):
What is clear is that the central city experienced much larger traffic volume reductions than other parts of Melbourne, which makes sense as office workers stayed home, universities, cafes, restaurants and night-life closed, and (non-essential) retail activity slowed considerably.
There is some noise in the variations by distance from the CBD but I suggest not too much should be read into that as there will be various local factors at play.
Traffic signal data comes out pretty much daily, so I will try to update this analysis periodically during the recovery.