Page:UK Traffic Signs Manual - Chapter 8 - Part 2- Traffic Safety Measures and Signs for Road Works and Temporary Situations) - Operations 2009.pdf/24

OPERATIONAL ISSUES

When provision is made for vehicles to travel outside the normal limits of the carriageway or hard shoulder (e.g. if a part of the verge is hardened for a short-distance in order to accommodate the necessary traffic lanes on that part of the highway), there should be a clearance of at least 0.6 m between the edge of the trafficked lane and the nearest part of any permanent traffic sign. Additional safety barriers may be necessary. O3.2.19 The minimum headroom to be provided at temporary structures (e.g. scaffolds, falsework, temporary accesses, etc.) should always be as follows:
 * where the temporary structure is free-standing, the minimum headroom should be as for sign/signal gantries, i.e. 5.41 m;
 * where the temporary structure is attached to or associated with a permanent structure, the minimum headroom for the temporary structure should be the same as for the permanent structure – if the permanent structure has a clearance greater than that given above, the minimum headroom for the temporary structure should be 5.41 m unless it is a high-load route; and
 * where the road has a high-load clearance requirement greater than 5.41 m, the headroom appropriate to the high-load route plus 0.15 m should be provided.

The headroom should always be increased as necessary to allow for vertical curvature, cross fall and the longitudinal grade of the road and take account of the deflection of the temporary structure under dead and live loads. If the required headroom is not obtainable over the full width, the part of the carriageway beneath the temporary structure should always be closed. The Highway Authority may use its powers to divert traffic when the required headroom is not available. 22