Performance Assessment of the 2010 HCM and Its Calibrated Model in Estimation of Weaving and Non-weaving Speed

Calibration is a conventional method which is utilized to adapt traffic models based on local situations in order to achieve best results. One of the issues regarding the efficiency of this method is whether traffic models should be calibrated only in one or two major cities of a country or calibrated based upon a comprehensive selection of cities. Therefore, this study, which has used the actual speeds, attempts to evaluate the performance of the weaving model that was proposed in the fifth edition of Highway Capacity Manual (HCM 2010) and its calibrated model, which was calibrated in Tehran highways. In this regard, adequate field-data were collected on a ramp-weaving segment in Isfahan. The procedure was of 9 fifteen-minute time steps of recording at different hours of a working day. The analysis results indicated poor and appropriate performances by the HCM 2010 model in estimating speeds of non-weaving and weaving vehicles, respectively, for which the RMSE (Root Mean Square Error) values were obtained as 16.34 km/h and 2.11 km/h, respectively. Moreover, not only was the calibrated model unable to improve the performance of the original model, but also it affected the original model negatively and caused a larger difference in the model output compared to the actual values. Hence, calibrated models based on metropolises such as Tehran may not necessarily be applied to other cities and may lead to unrealistic results. This reflect the fact that traffic patterns in two cities of one country may be highly dissimilar.