Work on the development of speed reducing road humps carried out at TRL resulted in a circular (round-top) hump profile which has been successfully used on roads in many countries. Since the 1980's the regulations governing the use of road humps in England and Wales have been gradually relaxed to allow greater flexibility in the shape of humps so as to include flat-top humps, raised junctions and speed cushions. The current regulations do not specify an exact hump profile providing the humps are between 25 mm and 100 mm in height, at least 900 mm long and with no vertical face exceeding 6mm. Humps with a sinusoidal profile have been reported as being more comfortable for cyclists, and possibly also for car drivers, but there has been little information as to the relative difference between the profiles regarding their impact on noise and ground-borne vibration levels. In order to improve the advice available to local highway authorities, the Charging and Local Transport Division of DETR commissioned TRL to undertake a comparative evaluation in terms of passenger/rider discomfort, vertical acceleration, vehicle generated noise and ground-borne vibration of a number of humps, all 75 mm high, but with different profiles. The five profiles used in the trials included three non-standard profiles: a 3.7m long hump with a sinusoidal profile, a 5m long round-top hump, and an 8m long flat-top hump with sinusoidal ramps. Two frequently used hump profiles were included for comparison: a 3.7m long round-top hump and an 8m long flat-top hump with straight ramps. All humps were installed on the TRL test track. This report gives details of the track trial at TRL and the results obtained from the measurements of noise and ground-borne vibration levels. The 'companion' TRL Report 417 (Sayer et al, 1999) gives details of the results of the measurements of passenger discomfort and peak vertical acceleration. (A)

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