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T.P.D.M.V.2.3
(Al/2001)
33.9 CMmbiag Lanes for Dual Carriageway Roads
3.3.9.1 An additional uphill lane should be provided on 2 lane dual carriageway roads if the forecast
design year traffic flow exceeds the flow level indicated in Diagram 3.3.9.1 relative to the
gradient of the hill The Gradient G = 100 H/L should be calculated in accordance with
Diagram 3.3.9.1. An additional lane should be considered if the minimum gradient is 3%
over a distance of 0.5 km.
3.3.9.2 Where costs of providing the additional land for a climbing lane are high relative to the total
cost of the works, consideration should be given to adjusting the alignment of the
carriageway within the standard highway width and reducing or eliminating the
verge/marginal strip widths so that a climbing lane can be provided without any additional
land being required, as shown in Diagram 3.3.9.2.
3.3.9.3 The appropriate full width of the climbing lane should be provided in similar manner to that
for single carriageway, i.e. at a point !I S", 100m from the 2% point of the sag curve.
However a taper of at least 1 in 45 should be provided in the case of climbing lanes for dual
carriageways, as shown in Diagram 3.3.9.3
3.3.9.4 At the end of the climbing lane section the extreme left hand lane should be continued, and
any tapering down should affect the extreme right hand lane as shown in Diagram 3.3.9.4.
3.3.9.5 Passing bays are not appropriate for dual carriageway roads.