Travel Times and Speeds
Speed Survey Data
The County Council undertake adhoc speed surveys, typically using automatic traffic counters or speed detection radar.
GPS Speed Data
The Department for Transport (DfT) provide GPS speed data to Local Authorities in the spring time on an annual basis. The data is provided to us by the DfT in 1-year batches and CCC therefore only hold speed data up to 31st Dec 2021 at present. Data for 2022 is expected to be available in Spring 2023.
The GPS speed data is collected from a sample of GPS tracked vehicles. The GPS data is used to calculate average speeds along short stretches of road known as links. The data covers all public local and strategic roads, however the number of speed observations is typically higher on larger roads and low numbers of observations can limit the robustness of the data on smaller roads. It is therefore important to be aware of the number of observations (sample size) being used to produce the average speeds for each of the links being analysed.
The DfT previously sourced the GPS speed data from Teletrac Navman (formerly known as Trafficmaster) but changed data provider to CTrack/Inrix as of 1st January 2021. The DfT have demonstrated that the new Inrix data results in inherently lower average speeds (or longer travel times) than the historic Teletrac Navman Data. It is therefore not recommended to directly compare the old and new GPS speed data.
BaseMap provide more information about the historic Teletrac Navman data in their TM Speed Data video. DfT have indicated that “the new Inrix data is provided to the same specification as the historic Teletrac Navman data” and the data collection method is therefore believed to be similar.
We are permitted to provide the raw data to consultants contracted to work on behalf of CCC/GCP, providing they have signed an Inrix Data Use Agreement. If you require any travel time or speed data to inform County Council projects, please contact policyandinsight@cambridgeshire.gov.uk, and we will assist where possible.