1.0 Purpose of Report
1.1 To advise Members of the outcome of a review of our current policy regarding the introduction of 20mph speed limits.
2.0 Background
2.1 A review of the current 20mph speed limit policy has been carried out which takes into account the latest guidance published by the Department for Transport and best practice and addresses the feasibility of introducing variable speed limits outside schools. This review will be considered by the Transport and Telecommunications Overview and Scrutiny Committee on 29 November and their views will be reported at your meeting.
3.0 Discussion
3.1 The Department for Transport published new guidelines on setting local speed limits in August 2006. This guidance states that “the aim should be to align the local speed limit so that the original mean speed driven on the road is at or below the new posted speed limit for that road.”
The guidelines also suggest that 20mph speed limits are only suitable where mean vehicle speeds are 24mph or below, or where additional traffic calming measures are planned. This differs from the previous guidance given by the Department namely that if observed 85th percentile speeds are above 24mph, then it is unlikely a 20mph speed limit would be appropriate, unless traffic calming measures can be provided. Our current 20mph speed limit policy complies with the previous guidance.
3.2 It is considered that our 20mph speed limit policy requires amending in order to make the guidance more specific and take account of the new national guidance and the new scheme prioritisation system contained in the second Local Transport Plan (LTP2). The policy has therefore been updated to reflect this and is attached as Appendix A. The changes from the previous policy are shown in italics in Appendix A. For purposes of comparison the current 20mph speed limit policy is attached as Appendix B.
3.3 North Yorkshire Police have been consulted on the updated policy and have indicated their support.
4.0 Variable Speed Limits Outside School
4.1 As a Highway Authority, we have the power to introduce variable speed limits under a Traffic Regulation Order.
4.2 Traffic Advisory Leaflet 9/99 states: “It is of doubtful benefit to have a short length of either a 20mph speed limit or a 20mph zone outside a school. Apart from the uncertainty of whether drivers will observe the limit, they may subsequently speed up significantly in an area where children, in relatively large numbers, will be approaching or leaving the school. Forming a self-enforcing 20mph zone in roads surrounding the school would be likely to reduce the frequency of accidents not only in the immediate vicinity of the school, but also on the routes that children take to school”.
4.3 Research in Scotland into the effectiveness of full time advisory 20mph speed limits in residential areas concluded that the majority of trial sites had not been successful in obtaining an average speed of 20mph although 60% of sites showed a reduction in speeds.
4.4 Traffic Advisory Leaflet 1/03: Vehicle Activated Signs advises that research on part time 20mph zones found that this measure as a speed reducing feature had little effect on vehicle speeds. Transport Research Laboratory (TRL) report 363 showed that the use of static signs only has a small effect on mean and 85th percentile speeds, and for 20mph zones this has been found to be about 1mph on average. Added to this, the cost of installation means that such measures offered poor value for money.
4.5 The cost of installing the variable message signs required for a variable 20 mph speed limit would be in the order of £50k per site. There would be a minimum of eight signs (two double faced terminal signs showing 20 and 30 at each end of the scheme) plus any repeater signs. The whole life cost is likely to be relatively high due to ongoing maintenance requirements. Permanent signs would require approval from the Secretary of State and GOYH have indicated that such approval is unlikely to be forthcoming.
4.6 In addition, a variable speed limit outside a school could be counter productive if speeds only reduced by about 1mph as parents and pupils may have a false sense of security due to the new speed limit which may lead to reduced awareness of traffic.
5.0 Conclusion
5.1 This review has considered the latest guidance and best practice with regard to 20mph speed limits and has concluded that an updated policy is required to reflect the need to make the guidance more specific and to reflect developments due to the second LTP.
The possibility of introducing variable speed limits outside schools has been considered but is not recommended due to the evidence suggesting that such limits would not have the desired speed reducing effect and would therefore not represent effective use of the limited funds available for highway schemes.
6.0 Recommendation
6.1 Members are asked to approve the updated policy for the introduction of 20mph speed limits attached in Appendix A to this report.
Gordon Gresty
Corporate Director, Business & Environmental Services