OPTIMISATION OF TRAFFIC CALMING SURFACES

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. The main application foreseen at this early stage was on the high-speed approaches to road hazards in mainly rural areas. For this reason resident's 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 and rumble devices were not generally recommended for roads in urban areas because of this issue. There is a need therefore to optimise TCSs so that the driver is alerted without consequential disturbance to residents. This paper reports on an ongoing 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 vehicle suspensions which were readily transmitted into the driver's cab. The paper describes the results of test track measurements of noise and vibration that has led to the identification of potentially suitable designs. (A) For the covering abstract see ITRD E113232.