Road congestion and reliability statistics

Road congestion and reliability statistics information.

Road congestion on locally managed ‘A’ roads is measured by estimating the average speed achieved by vehicles during the weekday morning peak, from 7am to 10am. Average speeds are presented at national, regional and local highway authority level.

Reliability on Highways England’s motorways and ‘A’ roads is measured by the percentage of ‘journeys’ that are ‘on time’, comparing journey times with historical data for individual sections of road. Statistics are presented at a national level and for individual junction to junction road sections.

Statistical releases on both measures in this series are published on a quarterly basis (in February, May, August and November). The statistical datasets supporting the road congestion on locally managed ‘A’ roads publications are updated on a quarterly or annual basis (in November). The datasets supporting the reliability on Highways England’s motorways and ‘A’ roads are updated on a monthly basis.

Technical information

These statistics used to monitor road congestion and journey time reliability are compiled from journey time data from in-vehicle global positioning systems (GPS) and flows estimated using automatic traffic counters and the department’s manual traffic count data.

The Road traffic, speeds and congestion statistics guidance contains a brief introduction into these statistics, including what they measure, how they are published and how they are used. The guidance also includes technical information relating to the reliability of journeys on the Highways England’s network and on locally managed ‘A’ roads, plus information on public attitudes and research and development.

The Road congestion and reliability statistics table index lists all the tables relating to this series, including archived statistics.

National statistics

All of the statistics published in this series are National Statistics. Road congestion and reliability statistics were assessed by the UK Statistics Authority and confirmed as National Statistics in July 2012.

Raw data available for download

Pre-release access list

The post holders given access to these statistics up to 24 hours prior to release are available in the pre-release access list.

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Road congestion and reliability statistics enquiries

Data tables associated with this series

  1. Highway Agency motorways and 'A' roads: ‘on time’ journeys (CGN01)

    • Statistical data set
  2. Flow weighted vehicle speeds (CGN02)

    • Statistical data set
  3. Flow weighted vehicle speeds, by region (CGN09)

    • Statistical data set