Vehicle speed monitoring data: September 2023 to February 2024
This release summarises the vehicle speed data from selected monitoring sites across Wales. All roads monitored had a 30mph speed limit before 17 September 2023 and a 20mph speed limit from 17 September 2023 onwards. At the time of monitoring, all roads were largely free from physical restrictions or obstructions that reduce traffic speeds.
This data supersedes the preliminary data (20 February 2024).
The analysis is based on a total of eight weeks of speed monitoring, with four weeks pre-implementation (before 17 September 2023) and four weeks post-implementation (after 17 September 2023).
The pre-implementation monitoring took place over two, two-week periods in July and September 2023. Post-implementation speed monitoring occurred over a two-week period in November 2023 and two weeks in January 2024.
Summary
The data in this publication will be used to monitor progress against the following three Key Performance Indicators (KPIs), outlined in the national 20mph monitoring framework (September 2023).
Percentage traffic compliance with the 20mph speed limit (KPI 1.1)
For the purpose of KPI 1.1, anyone driving at or below 24mph is categorised as compliant with the new speed limit. Across all monitoring areas and sites, 57.8% of vehicles were travelling at or below 24mph following the introduction of the default 20mph speed limit on restricted roads. Before the introduction, 20.2% of vehicles were travelling at or below 24mph.
Change in 85th percentile speed (KPI 1.2)
The 85th percentile speed, weighted by total vehicle volume, has decreased by 3.9mph, from 33.1mph to 29.2mph.
Change in the mean speed (KPI 1.3).
The mean speed, weighted by total vehicle volume, decreased from 28.9mph pre-implementation to 24.6mph post-implementation, a reduction of 4.3mph.
Vehicle speed distribution
Overall speeds have decreased. The proportion of vehicles recorded travelling at 15-19mph increased from 3.5% pre-implementation to 16.4% post-implementation. Similarly, the share of vehicles travelling between 20-24mph has increased by 23.6 percentage points to 38.9% post-implementation. The number of vehicles recorded travelling at 25-29mph, 30-34mph and 35mph and above have all reduced following the introduction of the default 20mph speed limit.
National implementation, data - February 2024
Preliminary weighted mean speed (mph) changes on main through roads following the national 20mph default speed limit on restricted roads
These data are preliminary. Further post-implementation data are being collected during 2024, so post-implementation speeds presented here will be subject to change. For this reason, caution is recommended when interpreting. The data are representative of the areas monitored but may not be representative of all of Wales.
The data were collected on main through roads at 43 locations in nine settlements. All roads monitored had a 30mph speed limit before 17 September 2023 and a 20mph speed limit from 17 September 2023 onwards. All roads were largely free from physical restrictions that reduce traffic speeds at the time of monitoring.
- Speed changes 20mph national rollout preliminary
(A revised version of the preliminary weighted mean speed (mph) changes was published on 1 May 2024, following a correction in the calculations for Table 1) - Monitoring site maps
Compliance with the Code of Practise for Statistics:
Default 20mph Speed Limit On Restricted Roads Phase 1 Areas - February 2024
Default 20mph speed limit on restricted roads - September 2023
Default 20mph Speed Limit on Restricted Roads Phase 1 - March 2023
Contact details for this report
Geospatial and Strategic Transport Analysis Unit
