The Department for Transport does not hold data on congestion by constituency.
For the strategic roads network in England congestion is monitored using journey time reliability. Journey time reliability is the average delay for the slowest 10 per cent. of journeys measured over the period of a year. Delay is calculated as the difference between observed journey time and a reference journey time (the time that could theoretically be achieved when the traffic is free flowing).
Reliability has only been monitored since the year August 2004-July 2005. Since that time, delays for the slowest 10 per cent. of journeys have increased from 3.78 minutes per 10 miles to 3.92 minutes per 10 miles in the year June 2007-to May 2008. The yearly figures are shown in the following table.
Period Delay for strategic roads in England (minutes per 10 miles) August 2004 to July 2005 3.78 August 2005 to July 2006 3.78 August 2006 to July 2007 4.19 June 2007 to May 2008 3.92
For the large urban networks congestion is monitored through change in peak period speeds. The following table shows peak period speeds across large urban areas in England in 2002, 2004 and 2006, based on surveys conducted by this Department and Transport for London:
2000-03 2003-06 2006-09 London Central 9.9 10.6 9.3 Inner 11.6 11.7 11.2 Outer 16.9 16.3 —
2002 2004 2006 West Midlands 21.1 20.5 18.9 Greater Manchester 23.2 21.0 18.5 Leeds/Bradford 20.1 20.4 20.8 Tyneside 27.8 24.7 25.5 Merseyside 23.7 19,8 18.7 Sheffield 18.8 18.6 19.0 Bristol 23.2 19.0 20.2 Nottingham 15.9 16.4 16.5 Leicester 15.6 14.7 15.8 Stoke/Newcastle-under-Lyme 24.3 16.0 17.8 Teesside 36.2 33.1 35.9 Hull 18.8 20.0 21.5 Bournemouth/Poole 21.0 19.4 19.6 Brighton/Hove 27.0 29.6 29.7 Plymouth 23.3 22.0 20.3 Southampton 16.7 19.5 17.7 Blackpool 18.8 19.4 19.7 Portsmouth 25.8 27.5 28.5