Page:Report of the Traffic Signs Committee (1963).pdf/73

 lane. The right distance from the junction will depend on the length of the traffic queues which normally form at the signals.

266. Where it is necessary (see paragraph 90) to supplement a Roundabout sign (figure 36) with a plate reading Reduce speed now (figure 36a) the sign should be placed on the central reservation at a point about 500 yards from the roundabout and repeated on the nearside verge at a distance of about 440 yards from the roundabout.

267. Intermediate waiting restriction and clearway signs should be provided near to and on both sides of any junctions along a restricted road and clearway so as to be readily seen by drivers entering it from the side road. Where the signs are supplemented by carriageway markings and provided there are no junctions, the permissible spacing between adjacent signs should be 300 feet for normal waiting restriction signs, and 400 feet for signs on peak- hour clearways. Where no carriageway markings are used with waiting restriction signs the present permissible spacing of 200 feet should be retained. Signs on clearways (other than those which apply only during peak hours) should have permitted intervals of a mile.

268. The height at which signs are mounted is also important. Broadly, signs should be set at the eye-level of a driver in an average private car and we recommend that the lower edge of the sign should be 3 to 5 feet above the highest point of the carriageway. In urban areas signs liable either to be obscured by pedestrians or to obstruct them will have to be set above their heads and in this case we recommend a clearance of 6 feet 9 inches above ground level. But it will often be possible to place signs, particularly flag type direction signs, at the edge of the footpath, for instance on guard rails as is widely done abroad. Here they will not normally be obscured by pedestrians and, in the light of local circumstances and the volume of traffic, some risk of obscuration by vehicles should be accepted. These low-mounted direction signs can if necessary be supple mented by signs at a higher level. An advantage of the higher signs is that they can be given independent direct illumination whereas signs on guard rails cannot because of the risk of damage to the lamps.

269. Apart from those mounted above the road, signs should normally be placed on the nearside of the carriageway though there will be certain obvious exceptions such as the Keep left sign and those attached to traffic signals located on central refuges. There may also be exceptions in one-way streets and on dual-carriageways where signs are required on the central reservations.

270. Adequate clearance should be provided between the nearside edge of the sign and the edge of the carriageway. It is impossible to give firm criteria because so much depends on actual site conditions, but in urban areas the clearance should never be less than 1 foot 6 inches. On high speed dual-carriageway roads it should be 4 feet or more.

271. Care should be taken to ensure that signs are not so sited as to be obscured by existing structures nor liable to be overgrown by trees, hedges or