Road Traffic and Congestion in Great Britain: Quarter 1 2009

This statistical bulletin includes statistics on Road Traffic and Congestion in Great Britain Q1 2009 according to arrangements approved by the UK Statistics Authority. This bulletin includes first release of the following National Statistics:

Provisional estimates for road traffic in Great Britain for the first quarter of 2009.
Provisional estimates for inter-urban congestion in England for the year ending March 2009.

The bulletin also includes revised official statistics on congestion in ten major urban areas in England for the academic year 2007/08, which were updated on 25 June 2009, and provisional quarterly figures for the quarters ending November 2008 and February 2009.

Road traffic in Great Britain

The latest provisional figures show a decrease of 3.5 per cent in overall traffic levels between the first quarters of 2008 and 2009. Around 1 percentage point of this fall is attributable to the heavy snowfall, mainly during the first week of February.

The bulletin includes provisional traffic estimates broken down by vehicle type and road class. Key results include:

Between the first quarters of 2008 and 2009:

Car traffic decreased by 3 per cent.
Light van traffic decreased by 2 per cent.
Heavy goods vehicle traffic decreased by 12 per cent.
Traffic on motorways decreased by 5 per cent.
Traffic on rural ‘A’ roads decreased by 4 per cent.
Traffic on urban ‘A’ roads decreased by 2 per cent.
Traffic on minor rural roads decreased by 3 per cent.
Traffic on minor urban roads decreased by 3 per cent.

The Q1 2009 estimates are provisional. Final estimates will be published in Summer 2010 and are likely to differ slightly from the provisional figures.

Inter urban congestion in England

This quarterly bulletin also includes National Statistics on congestion on motorways and trunk ‘A’ roads in England used to monitor the PSA measure on inter-urban congestion. Between the CSR07 baseline year ending March 2008 and the year ending March 2009, provisional figures show that:

Average vehicle delay on the slowest 10% of journeys fell from 3.90 to 3.42 minutes per 10 miles.

Congestion in major urban areas in England

This bulletin contains revised statistics for monitoring the PSA target on urban congestion. Some changes have been made to improve the way in which we calculate the person journey time, and the method has been changed to reflect this.

2007-08 person journey times across the ten largest urban areas were 3.1 per cent faster than the baseline. In the baseline year the average person journey time was 4 minutes 15 seconds per mile, falling to 4 minutes 7 seconds per mile in 2007-08. Over the same period, person miles travelled fell by 2.4 per cent.
Across the ten urban areas, the average vehicle journey time per mile was 3 minutes 35 seconds per mile in the quarter ending February 2009. This is 2 per cent faster than the quarter ending February 2008.

Notes

Road traffic in Great Britain

1. The provisional quarterly and annual traffic estimates are based mainly on data from 180 Automatic Traffic Counter (ATC) sites. Caution should be taken in drawing conclusions about longer term trends from the estimates for a single quarter or year.

2. The final annual road traffic estimates are calculated from data collected by both the ATCs and around 10,000 12-hour manual counts, combined with road lengths. The final annual traffic estimates for 2008 will presented in the annual bulletin Road Statistics 2008: Traffic, Speeds and Congestion, due to be published in June 2009.

3. Traffic levels are measured in terms of vehicle kilometres and are sometimes known as the volume of traffic. This is not the same as congestion. For example, traffic levels could increase without increasing congestion if traffic were more evenly spread during the day, with less during peak periods and more at other times.

Inter urban congestion in England

4. The indicator used to monitor inter-urban congestion is the average vehicle delay in minutes per 10 miles (derived from the differences between observed journey times and a reference journey time) experienced on the slowest 10% of journeys for each monitored route. Currently, because of data quality considerations, 95 of the 103 routes are used to monitor network performance. More information can be found at: http://www.dft.gov.uk/pgr/statistics/datatablespublications/roadstraffic/speedscongestion/congestiononthestrategicroad5359

5. The data quality for all 103 routes was reviewed prior to the release of data for October 2008. Improvements in data quality allowed an additional five routes to be included for the year ending March 2008 onwards, but deterioration of data on one route (M1 J6a-13) in 2008 led to it being temporarily excluded. As a result the total number of routes included increased from 91 to 95 routes for the year ending March 2008 onwards. The previously published data for years ending March 2008 to September 2008 were revised, and there is now a small discontinuity with earlier periods.

6. The effect of the increase in the number of routes was to change the baseline figure of average vehicle delay for the year ending March 2008 to 3.90 minutes per 10 miles for 95 routes, compared with 3.95 for 91 routes.

7. This indicator is one of four used to measure success against the Department’s current 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. Reliability performance will be assessed in the context of an expected increase in traffic of 1 - 2% per year. There is no specific numerical target.

8. The data for March 2009 are provisional because there has not been full quality assurance at a route level, but it is unlikely that they will be revised. Provisional data for April and May 2009 will be published on 4 June and 2 July 2009 respectively.

Congestion in major urban areas in England

9. Congestion in urban areas is measured by “person journey time per mile”. The Department’s urban congestion PSA target states that by 2010-11, the ten largest urban areas will meet the congestion targets set in their local transport plan relating to movement on selected main roads into city centres. The target will be met if person journey times across the ten largest urban areas overall increase from the baseline by no more than 3.6 per cent by 2010-11, in the context of travel volumes increasing by 4.4 per cent.

10. The urban congestion baseline uses data from both 2004-05 and 2005-06.

11. The volume of travel is the number of people using the roads, rather than the number of vehicles.

12. The figures in this publication have been revised since being published in February 2009, reflecting minor technical changes in the way in which the statistics have been calculated.

13. This bulletin also includes a quarterly vehicle journey time series up to the quarter ending February 2009. Vehicle journey times are the average journey time per mile for cars, light vans and heavy goods vehicles, taking into account the number of vehicles on the roads but not vehicle occupancies. This measure allows for quarterly monitoring of congestion. The measure of person journey times only allows annual monitoring as some components of the person-based indicator are not available quarterly.

14. The urban congestion data are not yet designated as National Statistics. These data are official statistics that are under development and are being tested for their ability to meet user needs.

15. More detailed information about the methodology used for the calculations is published in the Urban Congestion PSA Indicator Technical Note, published on the DfT website at:
www.dft.gov.uk/about/howthedftworks/psa/spendingreview2004psatargets2