Methods for the removal of surface water from rural trunk roads

This report reviews established methods of trunk road drainage together with any promising new systems. The review was restricted to obtaining information on established drainage that would give a broad indication of systems and their performance across the country and at the same time allow identification of particular matters where information was lacking or further research was required. Information concerning the amount of maintenance required for the different systems was sought and was used in assessing the whole life costs of the systems. The degree to which earthwork or pavement failures could be attributed to drainage faults was also investigated. The main new system considered in the study was that put forward by Engineering Intelligence Division (EI) of DTp for the use of a triangular channel alongside the pavement to cater for surface water run-off. The suggested design involved separate provision of sub-surface filter drains for removing free water present from percolation through pavements or infiltration through verges. Drainage methods for rural trunk roads that are considered most favourable in the long term are indicated in the conclusions and suggestions made as to where research might be useful to fill gaps in current knowledge.