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Literature review of speed limits reduction report (FOI)

Literature review of speed limits reduction report (FOI)

Produced by the Freedom of Information office
Authored by Government of Jersey and published on 27 September 2023.
Prepared internally, no external costs.


This request follows on from the previous Freedom of Information request below:

Speed limits reduction report (FOI)


Please provide details of all the papers and materials considered in the 'literature review' which is referenced in the third paragraph of the answer, and describe how all these materials were moderated by the officers concerned. By 'moderate' one means how the officers assessed for ministers caveats in such reports including in particular those in the report attached to the earlier answer. Please include exactly what was put to Ministers about the problems of seeking to relate the findings of a large London-wide study to the very different circumstances at Jersey, including saying if no such analysis was put to them


Please also provide a copy of the report and assessment of the literature review that was prepared by officials, and a copy of the report about this presented to Ministers. Please say if, in fact, no such report was so presented to the latter.


Please explain what is meant by the clause at the end of the answer: "overall trends are being mirrored in Jersey with analogous data being provided" and provide a full copy of all the 'analogous data' that is referenced there together with the report on the same that was presented to ministers.


A and B

The sources of all the information reviewed as part of the referenced ‘literature review’ are listed below:

The relationship between impact speed and the probability of pedestrian fatality during a vehicle-pedestrian crash: A systematic review and meta-analysis (

Lustre: Lower Urban Speed Limits in Europe.pdf (

Cycling injury risk in London: A case-control study exploring the impact of cycle volumes, motor vehicle volumes, and road characteristics including speed limits (

Speed, emissions & health.pdf (

Air pollution: outdoor air quality and health (

The effect of speed bumps and humps on the concentrations of CO, NO and NO2 in ambient air (

Traffic Calming.pdf (

20mph Research Study - Process and Impact Evaluation: Headline Report (

National Heart Forum – Reducing the default speed limit in built-up areas.pdf (

South Central Edinburgh 20mph Limit Pilot Evaluation.pdf (

Go slow: an umbrella review of the effects of 20 mph zones and limits on health and health inequalities (

Why 30km/h?.pdf (

The literature review was conducted internally by Government of Jersey officers for their use only and were not presented to the Minister for Infrastructure.


The statement, “...overall trends are being mirrored in Jersey with analogous data being provided...”, means that the island’s collision data shows that within the town centre the Government of Jersey have also recorded a reduction in the number and severity of road traffic collisions involving cyclists since these roads speed limits were reduced to 20mph.

Locally within Jersey, collision frequency and severity has been analysed within two areas – the area within St Helier inside the ring road, where all roads were reduced to a 20mph limit in March 2019, and throughout the Parish of St Saviour, where widespread speed limit changes were made in November 2021, including reductions to 30, 20, and 15mph.

Excluding the period between March 2020 and May 2021, when traffic volumes and collision rates were not representative due to Covid restrictions, and comparing similar time periods before and after implementation (24 months for St Helier and 19 months for St Saviour), the headline results indicate the following:

St Helier

An overall reduction in the number of collisions in which people were injured of 35%, with a reduction of 16% in the number of collisions involving serious or fatal injuries.

A 32% reduction in collisions involving pedestrians and a 47% reduction in the number of collisions involving cyclists.

Although the number of collisions involving motorcyclists has not reduced, the percentage resulting in serious injury is down by 67% percent.

St Saviour

An overall reduction in the number of collisions in which people were injured of 18%.

A 24% reduction in collisions involving motorcyclists.

Although the sample size is relatively small, and other factors will have influenced the numbers of collisions, it is likely that the reduction in speed limits in St Helier areas has played a significant part in the reduction of collisions by 35% overall.

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