Seasonality in traffic flow

Monthly motor traffic profile

DfT has a network of permanent traffic counters across Great Britain, feeding into a range of traffic flow statistics. These include the annual demand profile for motor vehicles, presented for rolling five-year periods and split by road type and vehicle type. I’ve used this data to create these up-to-date* profile charts. (* pre-Covid – see below)

Firstly, charts showing the total traffic flow for all roads, urban roads, rural roads, and motorways. This is with the 2015-2019 data which is the most recent pre-Covid data. In all four cases, the winter dip is noticeable. For ‘all roads’ and rural roads, the profile is gently humped with most months being within 5% of the annual average. Motorway traffic is more strongly peaked, with its maximum in August. Urban roads show a complex profile with a clear dip August, similar in scale to the winter dip.

Bar chart of average daily motor traffic flow, by month, for all roads. GB 2018-2019, all roads, all motor vehicles. Index (% of average over entire period). The chart shows a humped distribution through the year, with less than 100% in the winter months and more than 100% in the summer months. The data are: Jan 91.7, Feb 96.4, Mar 98.8, Apr 100.7, May 102.9, Jun 103.9, Jul 103.3, Aug 101.7, Sep 103.1, Oct 101.6, Nov 100.4, Dec 95.5. Notes at bottom of chart are as follows. Source: DfT TRA0305. Contains public sector information licensed under the Open Government Licence v3.0. Commentary, terms of use and more resources: www.grahamjames.co.uk.

Bar chart of average daily motor traffic flow, by month, for urban roads. GB 2018-2019, all roads, all motor vehicles. Index (% of average over entire period). The chart shows a complex distribution through the year, with less than 100% in the winter months and August, and more than 100% in the remaining months. The data are: Jan 95.6, Feb 98.7, Mar 101.0, Apr 100.6, May 102.6, Jun 103.0, Jul 100.5, Aug 95.9, Sep 101.4, Oct 101.1, Nov 102.0, Dec 97.8. Notes at bottom of chart are as follows. Source: DfT TRA0305. Contains public sector information licensed under the Open Government Licence v3.0. Commentary, terms of use and more resources: www.grahamjames.co.uk.

Download full-resolution version of these charts (.png, 150k each): all roads, urban roads, rural roads, motorways . Terms of use

The matrix below splits the data by vehicle type as well as by road type. The left-hand column (headed ‘all motor vehicles’) corresponds to the bar charts above. The remaining columns break the data down into cars, light or heavy goods vehicles, motorcycles, and buses/coaches. These charts also include the two preceding five-year rolling periods (2013-2017 and 2014-2018) for completeness, although the differences between the three are minor^[1]. Motorcycle volumes have a particularly pronounced seasonality and so the vertical axis has been expanded for their charts.

Set of charts showing seasonal traffic patterns for motor vehicles, in a matrix of charts splitting the data by road type and by vehicle type. The data are average daily traffic flow, GB, by month, for five-year periods 2012-2016 to 2015-2019 (index as % of average daily flow across entire period). Going across the matrix, the charts are for all motor vehicles; cars and taxis; light commercial vehicles; HGVs; motorcycles (with an extended vertical axis as their seasonality is particularly strong); and buses and coaches. Going down the matrix, the charts are for all roads; motorways; rural roads; and urban roads. Each chart contains three lines, representing the periods 2012-2016, 2013-2017, and 2014-2018. In most cases the lines are hard to tell apart, although there are some minor variations. The small print at the bottom of the matrix reads as follows: Source: DfT TRA0305. Full data at https://www.gov.uk/government/statistical-data-sets/road-traffic-statistics-tra. Notes and definitions at https://www.gov.uk/guidance/road-traffic-statistics-information. Contains public sector information licensed under the Open Government Licence v3.0. Edition 1 (November 2024). Commentary, terms of use and more resources: www.grahamjames.co.uk.

Download A4-size PDF (200k) or medium-resolution .png file (172k) of these charts. Terms of use

Coming soon… has Covid affected this seasonal profile?

[1] There was a change in methodology between the 2012-2016 period data and the 2013-2017 period data; for clarity, the charts only show the data with the new methodology.