Speed reduction can form part of a traffic management option and should be considered at the works planning stage, especially in circumstances where the 1.2 metres sideways clearance required for speed limits of 50 mph or more cannot be maintained. Where this is the case, implementing speed control measures that reduce speeds to 40 mph or less can enable a smaller sideways clearance of 0.5 metres to be used.
Reduction of speed limit
Any reduction in speed limit must be supported by a Temporary Traffic Regulation Order.
Caution: To proceed with this option, your supervisor, manager or other competent person must consult the highway authority at the earliest opportunity. Where a temporary Traffic Regulation Order is required, sufficient advance notice must be given to the highway authority to enable proper application. Temporary Traffic Notices may be issued for emergency works and should be requested as soon as their need is recognised.
The use of a temporary speed restriction must be indicated by the display of the appropriate speed limit as part of the normal signing of the works.
Where a temporary speed limit is applied on a standard two-way road with shuttle working, the length of road covered by the temporary speed limit should include at least one chicane, and only positive types of traffic control should be used, e.g. Stop/Go boards or portable traffic signals.
Note that the advance signing layout must be appropriate for the permanent speed limit.
Use of chicanes
For short lengths of shuttle working, i.e. 50 metres or less, chicanes can be used to reduce traffic speeds to less than 10 mph. At least one chicane in each direction is required. The chicanes should be just large enough to allow a large vehicle to pass through slowly. Traffic must first be brought to a halt by positive traffic control and then released in small batches by careful use of Stop/Go boards or manually controlled portable traffic signals. Where it is not practical to provide a chicane in one direction, for example because there is a junction, an alternative traffic management arrangement should be used in that direction to ensure that traffic speeds are reduced to less than 10 mph, for example convoy working.
Warning: The planning, installation and operation of a chicane system must be undertaken by appropriately competent personnel.