Road Statistics 2008: Traffic, Speeds and Congestion

The Department for Transport has published the statistical bulletin Road Statistics 2008: Traffic, Speeds and Congestion according to the arrangements approved by the UK Statistics Authority. This bulletin includes the first release of National Statistics on 2008 Road Traffic in Great Britain, Free Flow Vehicle Speeds in Great Britain, and Traffic Speeds on the Strategic Road Network in England. The bulletin also includes further information about congestion on urban and inter-urban roads. Key results include:

Road Traffic in Great Britain

Between 2007 and 2008, total estimated motor vehicle traffic fell by 4.1 billion vehicle kilometres (0.8 per cent) to 508.9 billion vehicle kilometres. This is the first fall since 1979, but an 11 per cent increase over the decade from 1998.
Car traffic still accounts for the most significant share of the overall traffic, making up 79 per cent of all motor vehicle traffic. In 2008, car traffic totalled 401.7 billion vehicle kilometres. This is a 0.6 per cent decrease from 2007, and is up by 8.4 per cent since 1998.
Light van traffic fell for the first time since 1992. Light van traffic was 68.1 billion vehicle kilometres, a 0.4 per cent decrease from 2007, and is up by 34 per cent since 1998.
In 2008, heavy goods vehicle traffic was estimated to be 28.7 billion vehicle kilometres. This was a decrease of 2.2 per cent from 2007 and a 3.6 per cent increase from 1998.
In 2008, 28 per cent of traffic was on rural ‘A’ roads, 22 per cent on urban minor roads, 20 per cent on motorways, 16 per cent on urban ‘A’ roads and 14 per cent on rural minor roads.
In 2008, the South East of England was responsible for 17 per cent (87.1 billion vehicle kilometres) of all motor vehicle traffic in Great Britain.
In 2008, motorways and ‘A’ roads accounted for 0.9 per cent and 12 per cent respectively of the road length in Great Britain. In contrast, 20 per cent of all traffic was on motorways and 44 per cent on ‘A’ roads.
The minor (i.e. ‘B’, ‘C’ and unclassified) road length in Great Britain was estimated to be 344.2 thousand kilometres in 2008, amounting to 87 per cent of the total road length. These roads carried 37 per cent of all traffic.

Free Flow Vehicle Speeds in Great Britain

The reduction in overall traffic in 2008 does not appear to have changed average free flow vehicle speeds.
In the ten years from 1998, the percentage of vehicles exceeding the 30 mph speed limit in free flow conditions on built-up roads has dropped for every vehicle type. The most significant decrease was for cars. In 1998, 69 per cent of cars travelled at speeds in excess of the limit; by 2008 this dropped to less than half.
On motorways in 2008, 49 per cent of cars exceeded the 70 mph speed limit. In addition, 15 per cent of cars were recorded as travelling at 80 mph or faster.
Very few heavy goods vehicles exceeded their speed limit of 60 mph on motorways. However, over 85 per cent of them exceeded the 50 mph speed limit on dual carriageway non-built-up roads and over three-quarters exceeded the 40 mph limit on single carriageway non-built-up roads.
In 2008, over half of all motorcycles travelled faster than the 30 mph speed limit in built-up areas. Half of these (or a quarter of the total) exceeded the speed limit by 5 mph or more.
On motorways the percentage of cars travelling over 70 mph was at its lowest between 7 and 8 am and 5 and 6 pm. The drop in excessive speed at these times is likely to be due to an increase in traffic volumes during the peak periods.

Congestion and Traffic Speeds on the Inter-Urban Road Network in England

Average vehicle delay on the slowest 10% of journeys fell to 3.42 minutes per 10 miles from 3.90 minutes per 10 miles between the baseline year ending March 2008 and the year ending March 2009, a decrease of 12.3 per cent.
The average traffic speed over the whole network rose from 55.6 mph in 2005 to 55.9 mph in 2008, an increase of 0.5 per cent. The average speed for the weekday evening peak rose by 0.3 per cent. Speeds on motorways fell by 0.4 per cent and on dual carriageway ‘A’ roads speeds rose by 2.1 per cent. Roads experiencing all traffic conditions are included in these figures.

Congestion in English Urban Areas

The average person journey time in 2007-08 was 4 minutes 8 seconds per mile. This was 1 second per mile faster than 2006-07, and 8 seconds per miles (3.1 per cent) faster when compared to the baseline.
Average morning peak speeds on key routes in the ten largest urban areas vary considerably, both geographically and on a day to day basis. Thirteen per cent of monitored route segments achieve average speeds of 26 miles per hour or faster, and 41 per cent with average speeds of 15 miles per hour or slower.
The morning peak in congestion on the key routes is slightly less pronounced on Fridays than other days in the week. There is little or no morning peak on weekends or during school holidays.

Notes

1. Road Traffic in Great Britain - The figures that relate to traffic are measured in terms of vehicle kilometres; this is sometimes known as the volume of traffic, where one vehicle kilometre is equivalent to one vehicle driving one kilometre. This is not the same as congestion. For example, traffic levels might show an increase but at the same time congestion levels may decline. This could happen if, for example, there is more traffic overall but it is more evenly spread during the day, with less during peak periods and more at other times. Congestion has a number of consequences, such as causing delays and making journey times unreliable.

2. The road traffic estimates are calculated from data collected by some 180 Automatic Traffic Counters (ATCs) and 12-hour manual counts at approximately ten thousand sites per annum, combined with road lengths.

3. Free Flow Vehicle Speeds in Great Britain - Data for this survey are collated from 36 sites where a 30 or 40 mph limit applies and at 60 other sites. The sites have been selected so that speeds are not seriously constrained by road layout, traffic congestion or by the proximity of speed cameras. The speeds are recorded as vehicles pass over an automatic counter and do not represent speeds over a longer distance. They do however provide an indication of compliance with speed limits.

4. None of the survey sites in built-up areas were subject to a speed limit lower than 30 mph.

5. Free flow speeds represent speeds under conditions that normally unaffected by congestion. In contrast, the speeds provided in the chapters on urban and inter-urban congestion represent speeds under all conditions.

6. Congestion and Traffic Speeds on the Inter-Urban Road Network - The indicator used to monitor inter-urban congestion is the average vehicle delay, derived from the differences between observed journey times and a reference journey time (the time that could theoretically be achieved when the traffic is free flowing), weighted by traffic flows for each route of the Strategic Road Network (the inter-urban road network made up of motorways and trunk ‘A’ roads managed by the Highways Agency, as well as the M6 Toll). The slowest 10% of journeys are selected for each 15-minute departure time between 6 am and 8 pm for each day of the week, on each of 95 routes.

7. For the Comprehensive Spending Review 2007 (CSR07), this indicator is one of four used to measure success against the Department’s Public Service Agreement (PSA) to deliver reliable and efficient transport networks that support economic growth. The indicator will be monitored from the baseline year ending March 2008 up to the year ending March 2011. There is no specific numerical target. Data on progress with the inter-urban congestion PSA indicator are published monthly and quarterly.

8. Traffic speeds on the Strategic Road Network for 2005 to 2008 have been produced from the database used for the inter-urban congestion indicator.

9. Congestion and Traffic Speeds in English Urban Areas - Congestion in urban areas is measured by “average person journey time per mile”. The Department’s urban congestion PSA indicator monitors movement on selected main roads into city centres, for the largest ten urban areas. Progress on the urban congestion measure is published on a quarterly basis.

10. The person journey times and travel table (Table 6.1) in this publication reflects revisions made to Road Traffic and Congestion: Q1 2009, which was originally published on 7 May 2009.

11. The bulletin Road Statistics 2008: Traffic, Speeds and Congestion is available from DfT, SR2, Zone 3/17, Great Minster House, 76 Marsham Street, London, SW1P 4DR.