Page:UK Traffic Signs Manual - Chapter 3 Regulatory Signs. 2008 (Second Impression 2008).pdf/129



The sign shown in diagram 976 indicates the speed limit for tramcars in kilometres per hour. The sign, which is diamond in shape to distinguish it from signs for motor vehicles, may be used both on and off the public highway. Where trams run along the highway with other traffic, the sign would normally be used to indicate a lower speed limit for tramcars. Signs to diagram 976 might not be necessary where all traffic is subject to the same speed limit. The colour of the sign may be varied in accordance with the requirements of Her Majesty's Railway Inspectorate (HMRI). Further guidance on the use of the sign should be sought from HMRI.

To improve conspicuity against a complex or dark background, a speed limit sign may be mounted on a grey or yellow backing board (direction 42, as amended by the Traffic Signs (Amendment) General Directions 2004), although yellow backing boards will not normally be necessary when signs indicate an increase in the speed limit. A backing board can also make for a neater assembly, e.g. when the sign is mounted with the speed camera sign to diagram 879 (see figure 14-20). Other than when diagram 670 is mounted with a boundary sign to diagram 2402.1 (see para 14.51), any yellow backing board must be rectangular in shape (direction 42(6)). A sign to diagram 670 mounted on a yellow circular backing board is unlawful. A backing board must not itself be provided with a border of any kind, and no legend may be applied to it. Where it seems that a sign is not being noticed by drivers, it should be checked to ensure that it is well sited, not obscured by vegetation or other obstructions and is of the appropriate size and in good condition. Only then should the use of a yellow backing board be considered.

Figure 14-22 Example of a speed limit sign co—located with a boundary sign

Where a speed limit terminal sign to diagram 670 is mounted with a town or village boundary sign to diagram 2402.1 (not diagram 2403.1) a yellow backing board may be shaped to suit the assembly (direction 42(7)). Figure 14-22 shows a typical example. This arrangement is often used at village gateways. As drivers need to be made fully aware of the speed limit, the boundary sign has to be of a simple design to avoid being a distraction. A speed limit sign must never be incorporated within a boundary sign. If a speed limit terminal sign, to either diagram 670 or 671, is mounted back to back with the boundary sign, any irregularly shaped backing board facing drivers leaving the town or village must be coloured grey.

A yellow backing board may be reflectorised to increase its conspicuity at night. This should not usually be necessary on unlit roads, although it might sometimes be helpful on lit roads, particularly where the sign itself is unlit. It may also be fluorescent; this greatly increases conspicuity in dull weather and at dusk. Fluorescence can also be particularly effective in drawing attention to signs mounted in deep shadow, e.g. below overhanging trees. However, fluorescence is visually intrusive and should be used with 127