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T.P.D.M.V.2.3
(Al/2001)
3.3.6 Gradients
3.3.6.1 Whilst it is appreciated that topographical difficulties can influence considerably the
economics of a road scheme, gradients should on Trunk Roads, and Primary Distributors
conform with those given in Table 3.3.6.1.
Table 3.3.6.1
Maximum Gradients
Gradient
Type of Route Desirable Absolute
Maximum % Maximum %
1. Trunk Roads 4 8
Primary Distributors and Bus Routes
2. Others 5 10
3.3.6.2 For new roads with a design speed of 80 km/h or above, a desirable maximum gradient of
4% should be adopted.
3.3.6.3 For effective drainage with kerbed roads, a minimum gradient of 0.67% should be
maintained wherever possible. In flatter areas, however, the vertical alignment should not
be manipulated by the introduction of repeated reverses of vertical curvature simply to
achieve adequate surface water drainage gradients but alternative forms of edge drainage for
a level or near level road should be devised. For lower speed urban roads, drainage paths
may be provided by false channel profiles with minimum gradients of 0.67%, although for
high speed roads, other forms of continuous drainage may be necessary.