20mph speed limit

We have completed the first phases of a project to implement 20mph speed limits across most residential and shopping streets. The third and final phase, covering the West Central and South areas, of the project has now reached implementation stage.

This follows an extensive consultation exercise where the majority of respondents were found to support the 20mph speed control.

The overall public response to all of the consultations was in the region of 15%. Overall the results indicate that most respondees (71%) are in favour of the 20mph limit on residential and shopping roads.

It is intended that the new limits will be enforced using signs and road markings only. There will be no need for new road humps or any other physical speed management measures. ‘A’ and ‘B’ roads are generally not included; we intend to leave these at their existing speed limits.

The scheme has led to a reduction in recorded vehicle speeds since it was introduced.  Of those streets where average traffic speeds were previously above 20mph, some 93% have seen a reduction.

The project has an approved budget of £600,000 It is split into three phases, covering different areas of the city. The project map shows which areas each phase covers and highlights the roads that are not covered by the proposal.  20mph control across North area wards was completed in 2014 and across East area wards in winter 2015/16.  The implementation of the original Phases 3 & 4 is now combined to expedite delivery to complete in late 2016.

The maps below show the roads included in the 3rd Phase.

A draft implementation programme for the installation of the final phase 3 work is attached below:

Benefits of the proposal


There are many benefits to the introduction of a citywide 20mph speed limit. These include:
20mph speed control should help to encourage more people to choose to walk or cycle.

  • providing road conditions that encourage and facilitate the take-up of active and sustainable transport modes
  • making it easier for pedestrians to cross roads, particularly for children or the elderly
  • reducing the amount of road noise generated in residential areas
  • improving traffic flow, as it flows more smoothly through junctions at lower speeds
  • potentially reducing airborne pollution levels

The severity of injuries sustained as a result of road accidents can also be reduced when traffic travels slower. According to ROSPA, a pedestrian struck at 20mph has a 97% chance of survival. This falls to 80% at 30mph, and 50% at 35mph.

Monitoring of traffic before and after introducting the limit in north Cambridge showed that on average speeds reduced by 1-2mph. This is consistent with Department of Transport advice and the expectation of the Cambridge project.

20mph Project seminar presentations

A seminar covered a number of issues associated with 20mph speed limits in general, and in relation to Cambridge. The following presentations were given:

Case studies

Large-scale 20mph projects have recently been completed or are currently being progressed in a number of other cities. These include Bath, Edinburgh, Liverpool, Oxford and York.

The introduction of a 20mph speed limit in Bristol resulted in increased levels of walking and cycling. There has been no negative impact on bus journey times. Monitoring suggests that the introduction of a 20mph speed limit in Newcastle has reduced the number of road accidents.

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