20mph Zones and Limits


This page is an overview of the different types of 20mph zones and limits, the evidence for them, and RoSPA's policy statements. The full factsheet is available to download: 20mph Zones and Limits

There are still a high number of casualties on urban roads in the UK. In 2015, 747 people were killed, 15,517 were seriously injured and 133,753 slightly injured in reported road collisions on built up roads in Great Britain. A large proportion of these accidents occurred on residential roads, with 90 deaths on B roads in built-up areas and 292 deaths on other minor roads in built-up areas.

The majority of pedestrian casualties occur in built up areas: 20 of the 25 child pedestrians and 288 of the 383 adult pedestrians who were killed in 2015, died on built-up roads. Pedal cyclists are also vulnerable in built up areas, with almost half of cyclist deaths (48 of 100) and most cyclist casualties (17,252 of 18,884) occurring on these roads.

The Department for Transport's current guidance encourages and supports Local Authorities to implement 20 mph limits and zones in situations where there is a particular risk to vulnerable road users.

There are two distinct types of 20mph areas possible:

20mph zone

20mph zones, are designed to be "self-enforcing" due to traffic calming measures which are introduced along with the change in the speed limit. Speed humps, chicanes, road narrowing, planting and other measures are typically used to both physically and visually reinforce the shared nature of the road.

20mph limits

20mph limits, which consist of just a speed limit change but no physical measures to reduce vehicle speeds within the areas. Drivers are alerted to the speed limit with 20mph speed limit repeater signs.

20mph limits are most appropriate for roads where average speeds are already low, and the guidance suggests below 24mph. The layout and use of the road must also give the clear impression that a 20mph speed or below is the most appropriate.

Effectiveness of 20mph speed limits and zones

A large number of evaluation studies have demonstrated a link between the introduction of 20mph zones and a subsequent reduction in casualties. The size of the reductions and the consistency of results over a wide number of areas are further evidence for this link.

There is similarly strong evidence showing the benefits of traffic calming measures, which are used in 20mph zones.

20mph limits without traffic calming also reduces traffic speed, although this effect is smaller than when they are introduced with traffic calming or other measures. Their lower cost means that wider areas can be covered.

As well as road safety benefits, it is important to highlight the contribution that 20mph zones can have in encouraging more physical activity, such as walking and cycling, by contributing towards a safer environment. The money spent on the schemes can also greatly improve the character of a residential area and quality of life of the residents.

RoSPA's Policy Position on 20mph Speed Limits

20mph zones are very effective at preventing injuries and RoSPA would like to see their wider use in residential areas.

20mph zones significantly decrease the risk of being injured in a collision and their greater use, especially in residential areas, would help to reduce the number of traffic injuries in the UK.

Local Authorities are responsible for determining where 20mph zones and limits should be introduced but should take advantage of opportunities to introduce them where they are needed.

Consultation and engagement with local communities and other stakeholders is of vital importance, to make sure that safer roads are prioritised where needed and that local communities have input into the schemes development.

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