Page:UK Traffic Signs Manual - Chapter 8 - Part 1 (Traffic Safety Measures and Signs for Road). Designs 2009.pdf/11

INTRODUCTION "Relaxation" schemes are appropriate for certain types of works (as indicated within this Chapter) for short-term situations with good visibility and low traffic ﬂows. In this document "short-term situations" are situations that are expected to last less than 24 hours, "good visibility" means visibility extending to the full length of the stopping sight distance and "low traffic ﬂows" means ﬂows less than the reduced available carriageway capacity when the works are in place. "Stopping sight distance" is the distance required for a vehicle to come to a stop, taking into account the time taken to perceive, react, brake and stop safely – for full details see Table 3 of TD 9 "Highway Link Design" (DMRB 6.1.1). Individual plans state, where appropriate, what relaxations may be applied. Plans for single carriageway roads can be found in Section D5 and plans for dual carriageway roads in Section D6.

If relaxation schemes are located on roads with a permanent speed limit of 40 mph or more and are in place during the hours of darkness then warning lights must be added in accordance with the requirements given for the appropriate standard works. Additional signs may also be required to suit site specific circumstances. On roads with a lower permanent speed limit the use of warning lights should be considered, depending on the standard of street lighting.

The relaxations contained within this document are intended to retain fundamental signing principles whilst reducing the number of temporary traffic signs, road markings, and delineators. The general principle is that signing for relaxation schemes is a subset of signing for standard schemes, such that should conditions at the site deteriorate then additional signing can be added to bring the signing up to the level of the equivalent standard scheme. Alternatively, if appropriate, the site should be cleared. Due to the requirement for supplementary signing should conditions deteriorate, and the short-term nature of the works, relaxations should only be applied at works which are manned continuously.

Emergency traffic management should only be deployed for short-term incident management. 10