Wales’ first full year of 20 mph default limits shows early safety gains and speed reductions

Transport for Wales’ July 2025 National Monitoring Report offers the first comprehensive look at outcomes following the UK’s first nationwide introduction of a 20 mph default speed limit on restricted roads, implemented on 17 September 2023. The report – tracking data up to March 2025 – assesses eight key performance indicators across vehicle speeds, journey times, casualties and air quality.

Vehicle speeds falling and compliance improving

Vehicle speed data collected from 43 sites across Wales show that speeds have decreased and compliance has improved since the policy came into force. In winter 2024/25, 54% of vehicles were recorded travelling at or below 24 mph, compared with 21% before the limit was introduced, and 53% in summer 2024.

The 85th-percentile speed—the speed at or below which 85% of vehicles travel—fell to 29.5 mph, down from 32.9 mph before the change and 29.8 mph in summer 2024. The weighted mean speed was 24.9 mph, a notable drop from 28.7 mph pre-rollout.

Compliance has increased by +33.2 percentage points over baseline levels, and by +1.3 points compared to summer 2024, indicating sustained behavioural change among drivers.

Early signs of fewer casualties

Reported road casualties have declined in the first year since implementation. Across all road types, casualties fell by 11.8% in the 12 months following the change. On roads previously subject to 20 or 30 mph limits—those now covered by the new default—casualties decreased by 26.2%. In contrast, casualties on higher-speed roads (over 40 mph) increased slightly, by 4.2%.

However, the report notes that more time and data are needed before drawing conclusions on the policy’s effects on cyclist and pedestrian casualties. At least three full years of post-implementation data will be required to identify meaningful trends, in line with RoSPA guidance.

A milestone for European road safety policymaking?

These early findings show sustained reductions in speed and improved compliance, with no evidence of adverse impacts on air quality or journey times. While longer-term monitoring is essential, the initial data supports the case for low-speed environments as part of Europe’s strategy to reduce road deaths and serious injuries.