A model of speed profiles for traffic calmed roads

The influence of traffic calming measures on the speed of unimpeded vehicle s has been investigated by evaluating differences in speed profiles obtaine d from various combinations of traffic calming measures. A case study has b een conducted in the City of York (UK) focusing on traffic calming measures such as speed humps (flat-topped and round topped), speed cushions and chi canes implemented in sequence. Vehicles' passing times were simultaneously recorded at 16 points along each traffic calmed link. From these data a spe ed profile for each individual vehicle could be derived. An empirical model was developed using multiple regression analysis techniques based on data collected at three calibration sites. Speeds along these links were describ ed as a function of the input speed, the type of measure and the distance b etween measures. The speed profile model was shown to be a good representat ion for the data from the calibration sites. It efficiently predicted speed s of unimpeded vehicles over a given combination of traffic calming measure s in sequence. The validation process, based on data collected at three val idation sites, also indicated that the model provided a good representation of the observed profiles at these sites, with the exception of the predict ion of the effects of the chicanes on speeds. This type of measure was show n to produce diverse impacts on speeds which depended on the detailed desig n. While the model is a useful design tool, recommendations have been made for further enhancement to it. (C) 2000 Elsevier Science Ltd. All rights re served.