Early, mainly empirical studies on traffic calming surfaces (TCSs) at TRL led to the development of rumble areas and strips that were subsequently employed by local authorities to alert drivers to hazards ahead and where possible reduce vehicle speeds. The main application foreseen at this early stage was on the high-speed approaches to road hazards in mainly rural areas. For this reason residents reactions were not given high priority in these early trials although it became clear that there was considerable anecdotal evidence that noise disturbance occurred at some sites. More recently the environmental effects of introducing traffic calming surfaces into urban areas has become an issue. The need therefore arose to optimise TCSs so that the driver is alerted without consequential disturbance to residents. This report describes the various stages of a study where a more fundamental approach was taken to designing appropriate TCSs. This involved a consideration of vehicle resonances and the means of exciting these with a suitable road surface profile without the generation of significant external noise. It was found that for some surfaces significant horizontal vibrations were generated in the vehicle suspension which were readily transmitted into the drivers' cab. The report describes the results of test track measurements of noise and vibration and subjective evaluations that have led to the identification of potentially suitable designs. Finally the results of road trials at two sites are described where a social survey of residents was conducted, external noise measurements taken and vehicle speeds logged. (Author/publisher)
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