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T.P.D.M*V.2.4
4.3.8 Visibility Splays
4*3.8.1 Drivers approaching a priority junction from the minor road
should have unobstructed visibility to the left and right along
the major road, for a distance dependent on the major road
traffic speed, to enable them to judge safely when they may turn
into or cross the major road* This visibility also allows
drivers on the major road to be aware of traffic entering from
the minor road in time for them to be able to slow down or stop
safely should this be necessary.
4.3.8.2 The visibility should be available between points 1.05m above
the road level and provided by means of a visibility splay whose
area is defined by lines joining the points A, B and C as shown
in Diagram Mo. 4.3*8.1.
4.3.8.3 For roads within estates and other local roads of minor nature
or experiencing low speeds the distance AC above relating to the
50 km/h design speed may be reduced to 50m.
4.3.8.4 In difficult situations the dimensions AB may be reduced to 4.5m
and in exceptional circumstances 2m but the distance AC as
recommended above should always be provided. If AB is greater
than 15m high minor road approach speeds can be expected and
this situation should receive special considerations. (The
dimensions of lines AB and AC also govern the need for "stop"
control as opposed to "give way w control and more information on
this point is given in Volume 3 para. 2.3*2.4.)
4.3.8.5 Where the major road is a dual carriageway, with a central
reserve of adequate width to shelter traffic turning right from
the minor road, the visibility splay to the left should not be
provided, but the central reserve should be clear of
obstructions to the required distance as defined by dimension AC
and as depicted in Diagram No. 4.3.8.2. Similarly if the major
road is one way, only a splay in the direction of approaching
traffic is required.
4*3*8.6 In the vast majority of urban situations low major road speeds
are accompanied by wider footpaths. Additionally the high cost
of lane and intensity of development would provide ample
justification for the reduction of dimension AB to the 4.5m to
2m range. In such cases the required minimum distance AC would
be provided without any corner splay being applied to adjacent
buildings. In order to maintain adequate footpath widths in
these situations corner splays should be provided in accordance
with the standards set out in Diagram 4.3.8.3.