12ROAD SURFACE
UNEVEN ROAD
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May be used with diagram 577 or 570
12.1 The uneven road sign, diagram 556, is used to warn of danger arising from longitudinal or transverse irregularities in the road surface which at the normal speed of traffic might seriously impair control of a vehicle. The use of this sign should generally be regarded as temporary, pending remedial work to the carriageway. It should be removed when the defect has been remedied. A plate to diagram 511 "REDUCE SPEED NOW" and also the distance plate to diagram 570 (see section 18) may be used with it. The uneven road sign should not be used at level crossings where the rail levels make the road uneven; para 21.13 describes the use of diagram 782 for this purpose.
SOFT VERGES
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May be used only in combination with diagram 556.2
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May be used only in combination with diagram 556.1.
The distance may be varied or omitted (see Appendix C|)
12.2 The soft verges signs, diagrams 556.1 and 556.2, should never be used simply to discourage parking. They are intended to deal with problems where driving on the verge can damage drains or might result in vehicles becoming stuck or damaging the verge. For lengths greater than two miles, the sign should be repeated at intervals of approximately one mile.
SLIPPERY ROAD
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May be used with diagram 570
12.3 The slippery road sign, diagram 557, is intended for use where the danger of vehicles skidding is greater than normal. The distance plate to diagram 570 may be used with this sign (see section 18). The degree of danger cannot be precisely defined as this depends upon skid resistance value, speed of traffic and the degree of superelevation on bends. It is for the traffic authority to judge whether overall conditions are sufficiently sub-standard that special warning is necessary. Detailed guidance can be found in HD 28 Skidding Resistance in Volume 7 of the Design Manual for Roads and Bridges (see para 1.3). Care must be taken not to over-use the sign, or its credibility will be undermined. Remedial works to improve the skidding resistance of the road surface or to improve drainage should be undertaken as soon as practicable and the signs removed on completion of the works.
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