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T.P.D.M. V.2.5
(Al/2002)
5.4.4 Transverse Yellow Bar Markings
5.4.4.1 This type of "additional speed control device", consist of 90 No. markings, 600mm in width laid
at right angles to the carriageway over a 400m length, with the spacing between successive
markings becoming progressively smaller as the hazard is approached.
5.4.4.2 The effect of the markings is to distort the driver's perception as to the actual speed being
travelled thus creating the impression that the vehicle is actually "speeding up" and so
encouraging the driver to slow down.
5.4.4.3 This type of "additional speed control device" can be used on high speed approaches to
roundabouts, toll booth, slip roads etc.
5.4.4.4 for any location its use should generally not be considered other than when the following
conditions occur:
(i)
(ii)
(iii)
the road should be a dual carriageway road, or a direct extension of a dual carriageway
road, as in the case of a slip road leading to a roundabout.
the road should be subject to a speed limit of not less than 70 km/h.
there should be at least 1 km of dual carriageway with no major intersections or severe
bends before the location.
(iv) for existing roads accident statistics should indicate that at the location speed or speed
misjudgment was a predominant factor.
5.4.4.5 Details of the actual marking and the setting out procedures are given in Volume 3, Chapter 5
and should be followed. Modifications to the arrangement to obtain a shorter length of markings
will not achieve the desired effect and therefore is generally not recommended. However where
there is insufficient length for the full set of markings to be laid on a slip road, some reduction is
acceptable, but there should be at least 50 No. of the transverse marks, i.e. Dl to D50, in
accordance with Table 5.6.5.1 of Volume 3, Chapter 5.
5.4.4.6 The markings must be laid in a suitable durable reflective material, and it is relevant to note that
assuming a two lane approach some 360 square metres to 400 square metres of material will be
required. Because of the large amount of material used the initial cost of providing the marking
will be relatively high. To remain effective replacement will be required every two to three
years, and on some roads even more frequently. Therefore because of the relatively high cost of
providing and maintaining these makings it is essential in order to justify this expense that the
usefulness of the marking at any particular location can be properly demonstrated.