Vehicle speed monitoring data: July 2023 to September 2024
Summary
Vehicle speed monitoring data September 2024
These statistics provide insights into vehicle speeds recorded at monitoring sites on main through roads across Wales. Monitoring has taken place where a 20mph speed limit now applies. The data summarise vehicle speeds against the three Key Performance Indicators (KPIs) outlined in the national 20mph monitoring framework. The data were collected from 43 monitoring sites on main roads across 10 areas. The data should not be taken as representative of average speeds on all roads with a 20mph speed limit.
Table 1: KPI assessment
|
KPI |
Key Performance Indicator | Summer 2023 | Winter 2023/24 | Summer 2024 |
|---|---|---|---|---|
|
1.1 |
Percentage travelling at or below 24mph¹ | 20.8% | 58.7% | 52.7% |
|
1.2 |
Weighted 85th percentile speed (mph) | 32.9 | 29.1 | 29.8 |
|
1.3 |
Weighted mean speed (mph) | 28.7 | 24.4 | 25.1 |
In summer 2024, 52.7% of vehicles recorded were travelling at or below 24mph. This is a reduction from the 58.7% of vehicles recorded in winter 2023/4. Before the change in speed limit, 20.8% of vehicles were travelling at or below 24mph.
The 85th percentile speed, weighted by total vehicle volume, in summer 2024 was 29.8mph. This is 0.7mph higher than the 85th percentile speed recorded in winter 2023/24 (29.1mph). The 85th percentile speed was 32.9mph before the 20mph speed limit changes.
The weighted mean speed recorded in summer 2024 was 25.1mph, 0.7mph faster than the weighted mean of 24.4mph recorded in winter 2023/24. Before implementation, the weighted mean speed across all monitoring sites was 28.7mph.
The summer 2024 data (see Table 2) show that speeds, as defined using the three KPI measures, have increased slightly compared to the winter 2023/24 period. However, they remain below the speeds recorded before the speed limit change.
Table 2: KPI assessment for Summer 2024
|
KPI |
Key Performance Indicator | Summer 2024 compared to summer 2023 | Summer 2024 compared to winter 2023/24 |
|---|---|---|---|
|
1.1 |
Percentage travelling at or below 24mph | +31.9 percentage points | -6.0 percentage points |
|
1.2 |
Weighted 85th percentile speed (mph) | -3.1 | +0.7 |
|
1.3 |
Weighted mean speed (mph) | -3.6 | +0.7 |
¹ Vehicles travelling at or below 24mph is considered compliant with the 20mph speed limit
The vehicle speed distributions (see Figure 1) show the increased vehicle speeds observed in summer 2024 compared to winter 2023/24. For the summer 2024 period, of the 52.7% of vehicles compliant with the 20mph speed limit, 14.9% of vehicles were travelling at or below 19mph. This is down from 19.2% in winter 2023/24.
There was an increase in the proportion of vehicles exceeding the speed limit by 10mph or more. In summer 2024, 16.0% of vehicles monitored were travelling at or above 30mph, an increase from 14.0% of vehicles recorded in winter 2023/24. However, before the implementation of the speed limit changes, 37.0% of vehicles were travelling at or above 30mph. Overall, speeds recorded in summer 2024 are slower than those recorded in summer 2023.
Figure 1: Distribution of vehicle speeds by monitoring period
Background information
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.
The analysis is based on a total of twelve weeks of speed monitoring in:
- Summer 2023 - four weeks of data pre-implementation covering two weeks in July and two weeks in September.
- Winter 2023/4 - four weeks of post-implementation data, covering two weeks in November and two weeks in January.
- Summer 2024 - four weeks of post-implementation data, covering two weeks in July and two weeks in September.
The summer 2023 and summer 2024 data compare like-for-like periods before and after the implementation of the default 20mph speed limit on restricted roads policy.
