The report describes a study by TRL for the Department of the Environment, Transport and the Regions, to review the methods available for managing speeds in urban areas. In particular it assesses the likely effect of introducing signs-only 20mph zones compared with the effect of those which are self-enforced by means of traffic calming measures. The study comprised three main elements: (1) collection of information on low speed limit zones in other countries which use signs only; (2) a review of the effectiveness of existing 20mph zones in the UK where physical measures have not been used; and (3) measurement of speeds at sites in new 20mph zones where signs were installed before implementation of physical measures. Results indicate that where speeds of around 20mph are desired in urban areas, traffic calming remains the best option to achieve this. Where funding or other reasons preclude its use, the use of only static signs appears insufficiently effective to reduce speeds to 20mph or to achieve accident reductions. Where signs-only schemes are used, small speed reductions and accident savings can be achieved if associated publicity and enforcement campaigns are also used. However, speeds are still likely to remain well above 20mph. (A)
Abstract