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T.PD.M.V.2.6
(Al/2002)
6.4.2 Directional Signs
6.4.2.1 Details of the design format for directional signs along Expressways are given in Chapter 3
of Volume 3, and will be similar to those for Directional Signs along Trunk Roads and
Primary Distributor Roads, except that the background colour of expressway signs should be
green as opposed to blue on non expressway signs. Details of colour of direction signs is
given in Section 3.2.5 of Volume 3.
6.4.2.2 Along Expressways it is preferable that wherever possible gantry or overhead cantilever
directional signs are used, with the exception of the signing of service areas where gantry
signs will seldom be justified. Overhead cantilever and roadside directional signs are
therefore appropriate.
6.4.2.3 Where roadside signs are used they will, as mentioned before, require the verge to be
widened to create sufficient space to accommodate the sign structure. The same may apply
to gantry and overhead cantilever signs but to a lesser extent. However it is most important
for all types of signs that allowance for the extra land that may be required is made at the
design stage, as otherwise the provision of adequate guidance to road users may be
prejudiced. The actual width required for this purpose will depend on the particular sign
being used, but for roadside signs, widths of 4000mm or more merely for the sign itself are
not uncommon. The overall space required for the sign will be greater than just the width
of the sign, to allow both, for the necessary clearances, as shown in Diagrams 6.4.1.3 to
6.4.1.5 to be achieved, and any working space that may be required around the sign.
6.4.2.4 Although this is a necessity in respect of directional signing for all road types, it is essential
with regard to Expressways that care is taken to ensure that directional signs are positioned
correctly in relation to the junction to which they refer, and such that they are clearly visible
to approaching drivers from the appropriate distance. Table 6.4.2,1 provides information
as to the location of signs on Expressways, Table 6.4.2.2 on the minimum clear visibility
distance requirements, and Diagram 6.4.2.1 illustrates the visibility envelope necessary for
roadside signs. Particular care should be exercised in sag curve situations, where a gantry
sign may be obscured by another gantry sign or overbridge.
6.4.2.5 Diagram 6.4.2.2 illustrates typical arrangements for gantry and roadside and gantry
directional signing but further information on this may be found in Chapter 3 of Volume 3,
and should be consulted.
6.4.2.6 To avoid the erection of additional structures and to reduce the possibility of signs being
obscured, the use of convenient overbridges should be considered as a possible alternative
for mounting overhead signs but due regard must be given to the suitability of the bridge
structure for this purpose.