Various types of drainage channels are used on carriageway edges to clear surface water. The channel is sometimes used on its own or may have an adjacent safety fence. The assessment of the effect of roadside drainage channels on vehicle handling and stability is the main subject of this report. Testing has been carried out by the Transport Research Laboratory for the Department of Transport's Highways Agency. Results from tests conducted on three different channel profiles are presented and discussed. Two cars and one motorcycle were used in the test programme. Both subjective opinions and objective measurements were used to assess the effect of the channels on vehicle handling and stability. The main finding is that there appears to be little difference in vehicle behaviour between any of the three profiles tested. It is possible, however, to rank the profiles in order of severity. A trapezoidal channel with 1:4.5 side-slopes was found to be the least severe and an asymmetric triangular channel with 1:1 and 1:5 side-slopes was the most severe. (A)

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