Every year the Welsh government publish data of all road accidents in Wales where speed and severity of  injury are recorded for each police force (https://statswales.gov.wales/Catalogue). The data for 2023 has just been released and is the first such data since the introduction of the national 20 mph speed limit. What does the data show and what observations may be drawn that could be of interest to residents and planners of similar schemes such as the one currently being deployed in Ilkley ? (Read to the end for an interesting aspect of the scheme).

The data is shown below in three graphs, A to C; A shows where a slight injury occurred, B a serious injury, and C where a fatality occured. The data is grouped by speed. Two sets of data are shown for each speed grouping; the orange bar shows data for 2023, and the blue bar shows the average for the four years 2019-2022.

Key takeaway: the data shows that 20 mph schemes do not reduce the number of accidents, the number of injuries recorded or the number of deaths. Below 30 mph (looking at the 20 mph and 30 mph groups together) the numbers have not changed much - there are more in the 20 mph group than in the 30 mph group than before, but overall they are very similar. Most crucially, the numbers for serious injury (B) and death (C) remain roughly the same. If the scheme was operating effectively, would we not expect to see a marked shift from fatalities to serious injury (C to B) and serious injury to slight injury (B to C) ?

In some ways this should not be surprising; earlier analysis showed similar outcomes. In Northern Ireland for example a study published in the British Medical Journal (BMJ) concluded:

Conclusion A 20 mph speed limit intervention implemented at city centre scale had little impact on long-term outcomes including road traffic collisions, casualties and speed, except for a reduction in traffic volume. Policymakers considering implementing 20 mph speed limit interventions should consider the fidelity, context and scale of implementation. 

Link to article: https://jech.bmj.com/content/77/1/17

A look at more of the detail:

For 2023, in accidents at speeds at and above 40 mph, the incidence of all injuries is broadly the same as the 4 year average. Details of the nature of these incidents are not recorded and they may be occurring on roads that are not restricted by the 20 mph limit.

At 20 mph and 30 mph the data show a different picture. Focusing on the data for accidents involving slight injury, the number of accidents recorded at 20 and 30 mph are not reduced after the introduction of the 20 mph limit: the 4 year average being 60/year (56+4) compared to 59 in 2023 (19+40) after the imposition of the 20 mph limit. Secondly, only 32% (19/59) of drivers involved in these accidents are driving within the 20 mph limit, the remainder above the limit. This suggests that 66% of accidents are above the speed limit. This must question the effectiveness of the 20 mph speed limit. Thirdly, the number of accidents recorded at 20 mph is nearly 5 times higher in 2023 compared to before the 20 mph limit.

Examination of the data for severe injuries reveals a very similar trend (B). More worryingly, the number of deaths recorded in accidents involving speeds of 20-30 mph was increased from an average of 27 before the change of limit to 31 after (C). 

The key take-home message is that 20 mph schemes do not reduce the number of accidents, the number of injuries recorded or the number of deaths.

The Welsh Labour government are trying to put a positive spin on these data, but they can’t.  The imposition of a national speed of 20 mph in Wales has not worked and may be more dangerous. This is why Welsh politicians are calling for the removal of the 20 mph limit on many roads. 

What does this mean for Ilkley and Ben Rhydding? Bradford will be carrying out a traffic survey to determine if the 20 mph scheme is working. If this shows that it is not working, as shown in Wales, then the project cannot be signed off and will not be enforceable. Can Bradford afford to rectify this, probably not and we will be left with an enormous white elephant. However, there may be a positive note. As recently confirmed by former Mayor Cllr Milner, under the terms of the contract between Bradford and Ilkley Town Council to provide 20 mph zones, we will not have to pay Bradford for a scheme that does not work! 

Analysis by Jim Gillespie, Paul Birch, and Peter Barron