The Department for Transport produces estimates of road traffic in Great Britain each year. This involves commissioning about 10,000 manual traffic counts each year. Each count lasts from 7am to 7pm on a weekday outside of holiday periods. The manual counts are combined with data from around 180 automatic traffic counters which count continuously throughout the year.
Data from both sources are combined to calculate annual estimates of the total distance travelled by type of vehicle, road class and geographical area.
The methodology used for the road traffic estimates was subject to a National Statistics Quality Review in 2006. This was published in January 2007 and is available at:
www.statistics.gov.uk/about/data/methodology/quality/reviews/transport.asp
It is estimated that vehicles in Great Britain travelled 63 billion vehicle miles on motorways and 256 billion vehicle miles on other roads during 2007. This is the most recent year for which data are available.
Further information and data for previous years are available at:
www.dft.gov.uk/pgr/statistics/datatablespublications/roadstraffic/speedscongestion/roadstatstsc/roadstats07tsc