Travel time measures for the Strategic Road Network: January to December 2021 report
Published 2 March 2022
Applies to England
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This publication is available at https://www.gov.uk/government/statistics/travel-time-measures-for-the-strategic-road-network-and-local-a-roads-january-to-december-2021/travel-time-measures-for-the-strategic-road-network-january-to-december-2021-report
About this release
This statistical release presents information about travel times on the Strategic Road Network (SRN) - the roads managed by National Highways. The measures in this release are estimated using in-vehicle Global Positioning Systems (GPS) observations.
Changes to data provider
The Department for Transport (DfT) went through an open procurement exercise and have changed GPS data providers. DfT has also adopted the same methodology as National Highways for the SRN following a collaborative exercise on developing their metrics. These changes are discussed in the methodology notes.
The SRN, in 2021
In 2021, activity on the road network continued to be impacted by events related to the coronavirus (COVID-19) pandemic. Take caution when comparing data with previous time periods.
On the SRN in 2021:
-
the average delay is estimated to be 8.5 seconds per vehicle per mile compared to speed limits, a 16.4% increase on the previous year
-
the average speed was 58.9 mph, down 1.8% from 2020
| Year | 2019 | 2020 | 2021 |
|---|---|---|---|
| Average speed (mph) | 58.0 | 60.0 | 58.9 |
| Average delay (spvpm) | 9.5 | 7.3 | 8.5 |
Figure 1: Average annual delay and annual speed on the Strategic Road Network per year (Table CGN0404a and CGN0405a)
Definitions
Average speed is in miles per hour and is an estimate of the physical level of congestion.
Average delay is in seconds per vehicle per mile and is the difference between speed limit and recorded average journey times.
Notes on the methodology and sample
These travel time measures are based on data matched to National Highways’ National Traffic Information Service (NTIS) network in England.
The SRN covers ‘A’ roads and motorways that are operated by National Highways.
SRN: average speed
For 2021, the average speed on the SRN was 58.9 mph. This is a 1.8% decrease on 2020, which means on average vehicles were moving at a lower speed in 2021 compared to 2020. Previously, the annual average speed had remained broadly stable from March 2016 up until March 2020 at between 58 and 59mph, decreasing by 0.5 mph (this is a 0.8% decrease over the period). However, between March 2020 to May 2020, the average speed increased steadily to 62.5 mph and has been steadily decreasing since, back to levels seen before 2020. While weekly road traffic figures show road traffic has returned to pre-pandemic levels, we see average speeds on the SRN still remain above their pre-pandemic figures.
Figure 2: Average speed on the Strategic Road Network (Table CGN0404a)
Further details on average speed on the SRN
This measure reflects the average speed of cars on the SRN across the entire day (24-hour period).
The measure weights speed observations from a sample of vehicles by the associated traffic flows so that it is representative of traffic volumes on the roads in different locations and at different times of day (as for average delay).
SRN: average delay
For 2021, the average delay on the SRN is estimated to be 8.5 Seconds Per Vehicle Per Mile (spvpm) compared to speed limits. This is 16.4% higher compared to 2020, which means on average there was notably more delay in 2021 compared to 2020. Previously, annual average delay had begun to increase from mid-2018, but decreased during the advent of the coronavirus (COVID-19) pandemic. Throughout 2021, average delay has begun to return to levels seen pre-pandemic.
Longer term trends typically show seasonality, particularly when we move to and from British Summer Time. The average delay is slightly higher when we move from Daylight Saving Time to GMT at the end of October, which might be attributed to darker mornings leading to people getting up later and therefore more people on the roads during peak times.
In April, when we move to British Summer Time, the average delay is slightly lower, which could be attributed to people getting up earlier as it is lighter so there are fewer people on the roads during peak times. While these trends were not observed in 2020, they appear to have reoccurred in 2021.
Figure 3: Average delay on the SRN (Table CGN0405a)
How delay is calculated
Consider a road section of 10 miles, with a free flow speed of 60 mph. If a vehicle was able to travel at the free flow speed, it would take 10 minutes to traverse this section of road. If, instead, the vehicle is only able to travel at an average speed of 50 mph, it would take 12 minutes to traverse the road section. As this would take an extra 2 minutes (or 120 seconds) to travel the 10 miles, the average delay for this vehicle per mile would be 12 seconds.
SRN: Subnational Transport Bodies (STBs)
What are STBs?
The STBs are transport bodies, formed of multiple local highways authorities to provide large-scale strategic governance of transport related matters. STBs are given statutory power through secondary legislation, with Transport for the North being the first.
Average Speed
Most STBs recorded an average speed over 58 mph in 2021, with Peninsula Transport being the only STB recording a speed above 60 mph. There is a small decrease on the 2020 figures, where only Greater London Authority recorded speeds below 59 mph.
Figure 4: Average speed by STB on the Strategic Road Network in England, 2021 (CGN0404b)
Average delay
Most STBs recorded an average delay of between 8.0 and 9.5 spvpm in 2021, with Peninsula Transport being the only STB recording delay below 8.0 spvpm at 6.5 spvpm, and Greater London Authority the only one exceeding 10 spvpm at 12.6 spvpm. Delay is noticeably increased on the 2020 figures.
Figure 5: Average delay by STB on the Strategic Road Network in England, 2021 (CGN0405b)
Travel time measures for sub-national transport bodies on the SRN are available from January 2019 onwards. The monthly average speed and average delay for SRN roads within STBs can be found in Tables CGN0404b and CGN0405b.
Data is available for combined authorities within the data tables CGN0404c and CGN0405c, Combined authorities do not cover the whole of England and therefore this data has not been mapped.
SRN: junction level measures
Average speed
Around half of junctions had an average speed over 60 mph in 2021. Around a fifth of junctions had average speeds of less than 45 mph such as the A27 in West Sussex or A49 in Herefordshire. Several roads in and around major cities, such as the A57 in Tameside, recorded average speeds of 40 mph or below. This may be due to the road type, as it is harder to achieve high speeds on single carriageways or where junctions and roundabouts are closer together.
Figure 6: Average speed on the SRN in England at a junction level to give more granularity, 2021 (CGN0404d).
Average delay
The average delay on individual junctions was less than 15 spvpm across England in 2021. Around major cities, the delay is closer to 20 spvpm. This could be due to the high demand on the network around them relative to their capacity.
Figure 7: Average delay on the SRN in England at a junction level to give more granularity, 2021 (CGN0405d)
Junction level figures
While changes in speed and delay between years may appear large in some cases, the variations should be interpreted with caution. When travel time figures are based on data from a single road, they are more sensitive to disturbances such as road works and other local events. Therefore, road level speed and delay are expected to have greater variation from year to year than national figures.
Travel time measures for individual junctions on the SRN are available from 2021. The annual average speed and average delay figures for individual junctions can be found in CGN0404d and CGN0405d.
Road level figures
Data is now also available at road level for 2021 and average speed and average delay figures can be found in: CGN0404e and CGN0405e.
Coronavirus (COVID-19) effect on congestion
The COVID-19 pandemic has had a marked impact on everyday life, including on congestion on the road network. Exploratory analysis was conducted last year to estimate the impact of the coronavirus pandemic on congestion. A fall in the number of vehicles on the roads could be seen from when the national lockdown was announced in March 2020, therefore data has been considered as “affected by the pandemic” from 12 March 2020. While the coronavirus pandemic continues to have an effect, most road traffic has trended back towards levels seen before the pandemic. More details on the effect of the pandemic on the road network can be found in the storymap included with the 2020 annual publication.
Context and user feedback
Measures for the Strategic Road Network (SRN) were developed as part of the first Road Investment Strategy (RIS1), which sets out a long-term programme for England’s SRN. Following user feedback this release has developed the statistics to include Subnational Transport Body level data for the SRN and local ‘A’ roads. Interactive maps for the SRN and local ‘A’ roads have also been developed using ArcGIS Online. We will continue to review the content and presentation of these statistics, which we expect to develop further over time. Please contact us using the details at the bottom of the front page with any feedback you have, or if you would like further information.
National statistics
Statistics on Road Reliability and Congestion were designated as national statistics in 2012 signifying that they are produced to the high professional standards set out in the Code of Practice for Statistics. They undergo regular quality assurance reviews to ensure they meet customer needs. Details of ministers and officials who receive pre-release access to these statistics up to 24 hours before release can be found in the pre-release access list.
Methodology and technical details
It is important to note that although there are figures for average speed and average delay on both networks, they are not directly comparable. A full explanation and further information on the data used, methodology, quality assurance and other sources of data can be found in the Background Quality Report.
| What do congestion statistics tell us? | Understanding the data | Important considerations |
|---|---|---|
| What comparisons can be made? | Trends across all years can be compared on the ‘SRN’ | Methodological differences prevent comparisons between road types, while seasonality makes quarter on quarter comparisons inadvisable. Details are available in the Background Quality Report |
| Interpreting average delay | Delay is recorded across all 24 hours of a day on a seconds per vehicle per mile (spvpm) basis. Delay here is compared to free flow conditions or the maximum speed limit journey time. This can be an indication of the relative congestion on the network. | Road users do not expect free flow conditions so consciously build in additional time for journeys. Delay may therefore be perceived as relative to expected conditions. |
| Interpreting average speed data | Average Speeds are weighted by road traffic flows to represent the volume of traffic at different locations and times of day. This can indicate the level of physical congestion on the network. | SRN average speeds only include cars. |
| Interpreting reliability measures | The reliability measures provide the additional journey time required to travel across one link compared to free-flowing conditions. | Reliability measures are calculated for the daytime hours (6am to 8pm). |
Request for feedback
We are keen to receive feedback from users of transport statistics. If you have any comments about how the statistics in this release are presented or analysed, please contact us using the details listed on the front page of this release.
Next update
The next tables in this series are expected to be published in June 2022. This will contain monthly, and annual (year ending) figures, for the period April 2021 to March 2022. This will include new figures for the period January 2022 to March 2022. The next written report is expected to be published in February 2023 and will contain annual figures for 2022.
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Road congestion and travel times
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