9.7 The last point at which a driver can read the lower part of an overhead sign is described by a sight line from the bottom of the sign inclined at 10° below the horizontal. The sign should be mounted so that no part of the gantry structure, including any luminaires, obstructs this sight line.
9.8 Where the sign assembly is set against an open sky, when viewed from any point between the minimum clear visibility distance and the 10° sight line referred to in para 9.7, an extra 2sw height is added to the top of the sign without adjusting the position of the legend or arrows (see figure 9-1). This provision is not necessary when there is a grey backing board at the top of the sign. Where a junction name is provided, the 2sw adjustment is made to that part of the sign, as shown in figure 9-4.
9.9 The only panels which may be used on gantry signs are the green, white or blue panels indicating a route of a different status. Figure 9-5 shows the design details for the inclusion of these panels on gantry mounted signs.
9.10 On a primary route, where the exit slip road leads directly to a non-primary route only, a white panel is used for the non-primary destination block. Where the slip road leads directly to both a primary and a non-primary route, a white panel is not used.
9.11 On a non-primary route where the exit slip road leads directly to both a primary route and a non-primary route, the primary destination block is shown in a green panel.
9.12 The Regulations do not permit the inclusion of the following on gantry mounted directional signs:
(i) warning signs
(ii) regulatory signs
(iii) distances to destinations
(iv) panels indicating tourist attractions, lorry routes, MoD establishments and cycle routes.
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