A new system for draining surface runoff from roads has been backed by the ~Highways Agency~. An agency advisory note encouraging contractors to use shallow grassed channels adjacent to roads in schemes, as a greener alternative to conventional road-drainage systems, will be published in the HA’s revised Design manual for roads and bridges later this month. It follows a successful eight-year trial of the hydraulic performance of the channels – shallower than swales for safety reasons – by HR Wallingford and TRL, which involved monitoring runoff depth for a channel built on the M2 in Kent. In a separate trial, vehicles straying into the channels were found not to handle dangerously or cause damage that could not be repaired easily.