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Q On a number of occasions, discussion
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has arisen over here on the question of gradients—the lack of uniformity in designation in reports (in some cases "one in (say) 5" or in others (say) 20 per cent). Furthermore, when it comes to very steep gradients—where this matters—it is not clear whether a 1 in 5 hill means 1 in Son the horizontal base of the triangle or 1 in 5 of the road surface travelled.
I am aware that proper surveying practice infers that the horizontal is, literally, the base factor, but is this always the position in the case of test reports?
A When a gradient of 1 in 5 is quoted it refers to a vertical rise in a horizontal distance. In other words the "5" does not refer to the actual distance on the road surface. When a percentage gradient is quoted 1 in 5 is equal to 20 per cent, 1 in 4 to 25 per cent and so on.