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Data Provider: Welsh Government National Statistics Volume of road traffic by road classification and year
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Volume of road traffic in Wales by class of road.

Last update
8 November 2017 8 November 2017

Next update
November 2018

Publishing organisation
Welsh Government

Source 1
Manual Traffic Survey, Department for Transport

Contact email

National Statistics

Lowest level of geographical disaggregation

Geographical coverage

Languages covered
English and Welsh

Data licensing
You may use and re-use this data free of charge in any format or medium, under the terms of the Open Government License - see

General description
The statistics refer to the volume of road traffic in Wales. Road traffic estimates for Wales are compiled by the Department for Transport on behalf of the Welsh Government. These estimates are based on the annual roadside manual road traffic counts carried out across Wales during the year. These roadside counts are combined with automatic traffic count (ATC) data and road lengths to produce overall traffic estimates.

Traffic estimates for major roads are based on a census of all such roads whereas traffic estimates for minor roads are estimated by calculating growth rates from a fixed sample of count points on the minor road network. Further details of the methodology are available from the DfT at the link below:

All surfaced roads are included in the estimates. The categories are: Motorways: Special roads reserved for certain classes of vehicle. The categories for major roads are: ‘A’ roads, with sub categories; Urban roads: Those within the urban boundaries of settlements with a population of 10,000 or more. Rural roads: All other non-motorway major roads. The categories for minor roads are: ‘B’ and ‘C’ roads and unclassified roads.

Traffic volume is measured using Vehicle Kilometres (VKM), which are calculated by multiplying the annual average daily flow of traffic by the corresponding length of road. For example, 1 vehicle travelling 1 kilometre a day for a year would be 365 VKM over a year.

The Data Dictionary provides a detailed breakdown description of the variables that are included in the categories.

Frequency of publication

Rounding applied
Data are rounded to two decimal places. For entries where there are no data " * ".

Statistical quality
These statistics are used to inform Government, businesses, media and society and are used internally for policy formulation and monitoring. There are no other comprehensive data sources to enable the production of statistics about traffic for Wales and Great Britain. Some specific uses include:
1. Welsh National Transport Plan monitoring indicators include these traffic flow data. The indicator measures the change in traffic flows for Wales as a whole and for individual local authority areas.
2. These data will also be used as part of the calculations to meet any requests for the casualty rate per volume of traffic over individual road links.
3. The national and local CO2 emissions, relating to transport, use these traffic flows estimates.

Road traffic estimates are based on the results of many 12-hour manual counts in every year which are grossed up to estimates of annual average daily flows using expansion factors based on data from automatic traffic counters on similar roads. These averages are needed so that traffic in off-peak times, at weekends and in the summer and winter months (when only special counts are undertaken) can be taken into account when assessing the traffic at each site. DfT now sort roads into 22 groupings (previously there were only 7). This allows a better match of manual count sites with automatic count sites. These groupings were based on detailed analyses of the results from all the individual automatic count sites and take into account regional groupings, road category (i.e. both the urban/rural classification of the road and the road class), and traffic flow levels.

Volume of road traffic, statistical release:

transport road traffic road classification