Motorway drainage trial on the M6 motorway Warwickshire

The objectives of this investigation were: a) to assess driver reaction to flooding of the hardshoulder produced by a modified system of motorway drainage; b) to compare the hydraulic performance of this drainage system with predictions from a theoretical study. Records of the variation of the depth of flow along the hardshoulder and the total flow from the test section were made for 26 storms. During the three month period of recording the hardshoulder was substantially flooded on a number of occasions. During the three year period that the trial was carried out, no complaints were received from road users, and no accidents were attributed to the flooding. A comparison between predicted and measured depths of flow was made for nine of the recorded storms. This showed that the theoretical approach predicted depths that were in good agreement with those that were measured. Charts have been produced, based on a 50 per cent summer storm having a one year return period, that enable the spacing of the gully outlets to be determined.