Related publications
The DfT produces traffic statistics which provide estimates of the vehicle miles travelled each year in Great Britain, by vehicle type, road category and region.
Data source
Road traffic estimates for Wales are compiled by the DfT 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 and the automatic traffic count (ATC) data, which are combined with road lengths figures to produce overall traffic estimates.
Definitions
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 DfT.
Traffic volume
Traffic volume is estimated using traffic counts data collected by DfT. Data from manual traffic counts are combined with data from automatic traffic counters to calculate annual average daily flows (AADF). These daily flows are combined with road lengths to calculate the number of vehicle miles travelled each year by vehicle type, road category and region. In this release estimates are presented as billion vehicle kilometers.
Vehicle type
The vehicle types identified are as follows.
Pedal cycles
Includes all non-motorised cycles.
Motorcycles
Two-wheeled motor vehicles, including mopeds, motor scooters and motorcycle combinations.
Cars and taxis
Includes estate cars, all light vans with windows to the rear of the driver’s seat, passenger vehicles with 9 seats or fewer, three-wheeled cars, motorised-invalid carriages, Land Rovers, Range Rovers and Jeeps. Cars towing caravans or trailers are counted as one vehicle
Buses and coaches
Includes all public service vehicles and works buses other than vehicles with less than 10 seats.
Light goods vehicles (LGVs)
All goods vehicles up to 3,500kg gross vehicle weight. This includes all car- based vans and those of the next larger carrying-capacity, such as transit vans. Also included are ambulances, pick-ups, milk floats and pedestrian-controlled motor vehicles. Most of this group are delivery vans of one type or another.
Goods vehicles (HGVs)
All goods vehicles over 3,500kg gross vehicle weight. Includes tractors (without trailers), road-rollers, box vans and similar large vans. A two-axle motor tractor unit without trailer is also included.
All motor vehicles
All vehicles except pedal cycles.
Road class
All surfaced roads are included in the estimates. The categories are:
Major roads
Motorways
Dual carriageways designed for fast traffic with access limited to motor vehicles, and with relatively few places for joining or leaving. The only motorway in Wales is the M4.
A Trunk roads
Part of the strategic road network owned by and operated on behalf of Government.
A County roads
All other A roads.
Estimates for A roads are also available with sub-categories for urban and rural roads on StatsWales. Urban roads are those within the boundaries of settlements with a population of 10,000 or more, and rural roads are all other non-motorway major roads.
Minor roads
B roads
Roads intended to connect different areas, and to feed traffic between A roads and smaller roads on the network.
Classified unnumbered
Relevance
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 are listed below:
- These data are used as a monitoring measure in the Welsh Transport Strategy (Transport for Wales). The indicator measures the change in traffic flows for Wales as a whole and for individual local authority areas.
- These data are used to calculate the casualty rate per volume of traffic.
- National and local CO2 emissions estimates, relating to transport, use these traffic flows estimates.
Accuracy
Road traffic estimates are based on the results of 12-hour manual counts taken between March and November, which are grossed up to estimates of AADFs 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. Roads are grouped into 10 strata based on the type of road, the location, and the estimated AADF.
Major roads (motorways and ‘A’ roads) are represented by a series of links, which are unique sections of road which make up the entirety of the major roads network. A location on each of these links is used to count vehicles. The scale of the road network means it is not possible to count traffic on every stretch of road every year, therefore, a rolling Census approach is taken for major roads. Where a manual count has not taken place in the reference year, growth factors are applied to the previous year’s AADF. Growth factors are calculated from the change between the reference year and the previous year from data from automatic traffic counters on similar roads. Once an AADF for the latest year has been calculated for all of the links of the major road network, the figures are combined with road lengths to produce estimates for the amount of vehicle kilometres driven in the year.
Minor road estimates are calculated differently to major roads. Due to the large number of minor roads, it is not possible to count them all, instead a representative sample of minor roads are counted each year. This means that the accuracy of estimates for minor roads is likely to be of a lower quality than for major roads. The sample of minor road sites that are counted each year are used to estimate the change in traffic levels between years. These figures are then applied to the previous year’s minor road traffic figures, as well as the change in minor road length, to calculate the minor road traffic estimates for the latest year.
Data on motor vehicle registrations are collected by the Driver and Vehicle Licensing Agency (DVLA) and published by DfT. The DVLA database is regarded as being virtually complete in terms of the number of licensed vehicles.
Timeliness and punctuality
The DfT published road traffic estimates for Great Britain in 2023 on 22 May 2024. Our release uses this road traffic data in this publication and normally follows about three months later, although we plan to shorten this gap in future.
Revision
The DfT carries out a minor road traffic benchmarking exercise approximately every 10 years, with the aim to improve the accuracy of traffic estimates for minor roads. This was undertaken in 2020 (included in our October 2020 publication) and included revisions to the minor road traffic estimates covering 2010 to 2018. A table detailing these revisions was published as part of our 2020 statistical release. For more information about the minor roads benchmarking exercise, please refer to the documentation from the 2019 exercise (DfT).
Accessibility and clarity
This statistical bulletin is pre-announced and then published on the Statistics and Research website. Road traffic data for Wales is published on StatsWales.
Comparability and coherence
The statistics presented here are from the DfT data collection and are fully comparable and coherent with the estimates for Great Britain.
Official statistics status
All official statistics should show the standards of the Code of Practice for Statistics (UK Statistics Authority).
These are accredited official statistics. Their designation was confirmed in February 2011 following a full assessment against the Code of Practice (UK Statistics Authority). They comply with the standards of trustworthiness, quality and value in the Code of Practice for Statistics.
It is Welsh Government’s responsibility to maintain compliance with the standards expected of accreditation. If we become concerned about whether these statistics are still meeting the appropriate standards, we will discuss any concerns with OSR promptly. Accreditation can be cancelled or suspended at any point when the highest standards are not maintained, and reinstated when standards are restored.
Statement of compliance with the Code of Practice for Statistics
Our statistical practice is regulated by the Office for Statistics Regulation (OSR). OSR sets the standards of trustworthiness, quality and value in the Code of Practice for Statistics that all producers of official statistics should adhere to.
All of our statistics are produced and published in accordance with a number of statements and protocols to enhance trustworthiness, quality and value. These are set out in the Welsh Government’s Statement of Compliance.
These accredited official statistics demonstrate the standards expected around trustworthiness, quality and public value in the following ways.
Accredited official statistics are called National Statistics in the Statistics and Registration Service Act 2007.
Trustworthiness
These statistics are compiled from a range of data published by the DfT. The DfT publishes road traffic statistics by region as part of its Road Traffic Statistics collection and vehicle licensing statistics as part of its Vehicles Statistics collection (DfT).
This bulletin and accompanying statistics are pre-announced on the Statistics and Research area of the Welsh Government website. Access to the data during processing is restricted to those involved in the production of the statistics, quality assurance and for operational purposes. Pre-release access is restricted to eligible recipients in line with the Code of Practice for Statistics (UK Statistics Authority).
Quality
The published figures provided are compiled by professional analysts using the latest available data and applying methods using their professional judgement and analytical skillset. Statistics published by Welsh Government adhere to the Statistical Quality Management Strategy which supplements the Quality pillar of the Code of Practice for Statistics (UK Statistics Authority) and the European Statistical System principles of quality for statistical outputs.
Validation checks are performed by Welsh Government statisticians and queries referred to the Department for Transport where necessary. The statistical release is then drafted, signed off by senior statisticians and published in line with the Welsh Government’s statement on confidentiality and data access which is informed by the trustworthiness pillar contained in the Code of Practice for Statistics (UK Statistics Authority).
It is Welsh Government’s responsibility to maintain compliance with the standards expected of accredited official statistics. If we become concerned about whether these statistics are still meeting the appropriate standards, we will discuss any concerns with OSR promptly.
Value
The purposes of this statistical release and the accompanying data published on StatsWales are to provide evidence for policy development and to inform the media and wider public about the changes to the volume of traffic on the Welsh road network.
You are welcome to contact us directly with any comments about how we meet these standards. Alternatively, you can contact OSR by emailing regulation@statistics.gov.uk or via the OSR website.
Well-being of Future Generations Act (WFG)
The Well-being of Future Generations Act 2015 is about improving the social, economic, environmental and cultural wellbeing of Wales. The Act puts in place seven wellbeing goals for Wales. These are for a more equal, prosperous, resilient, healthier and globally responsible Wales, with cohesive communities and a vibrant culture and thriving Welsh language. Under section (10)(1) of the Act, the Welsh Ministers must (a) publish indicators (“national indicators”) that must be applied for the purpose of measuring progress towards the achievement of the wellbeing goals, and (b) lay a copy of the national indicators before Senedd Cymru. Under section 10(8) of the Well-being of Future Generations Act, where the Welsh Ministers revise the national indicators, they must as soon as reasonably practicable (a) publish the indicators as revised and (b) lay a copy of them before the Senedd. These national indicators were laid before the Senedd in 2021. The indicators laid on 14 December 2021 replace the set laid on 16 March 2016. This release does not include any of the 46 national indicators.
Information on the indicators, along with narratives for each of the well-being goals and associated technical information is available in the Wellbeing of Wales report.
Further information on the Well-being of Future Generations (Wales) Act 2015.
The statistics included in this release could also provide supporting narrative to the national indicators and are used by public services boards in relation to their local well-being assessments and local well-being plans.
