Can Highway Capacity Manual Model Be Used to Estimate the Capacity of Modern Roundabouts in China? A Case Study in Nanjing

Abstract

Roundabouts have been used successfully throughout the world and are being used increasingly in China in recent years. The primary objective of this study is to identify if the current Highway Capacity Manual (HCM) capacity estimation method can be used to estimate capacity of modern roundabouts in China. To achieve this objective, data was collected from one modern roundabout in Nanjing area in China. Based on the field measured data, the authors estimated the critical headway and follow-up headway using the Siegloch method. With the estimated critical headway and follow-up headway, the HCM model was used to estimate capacity of the selected roundabout. A linear regression model was also developed based on the field data. The models were tested against the capacity measured in the field. Capacity estimation results of the HCM model and the linear regression model were compared. Model validation results showed that the calibrated HCM model yielded a MAPE of 15.7% while the regression model yielded a MAPE of 11.6%. The results suggest that the HCM model provides reasonable capacity estimates for roundabouts in China after crucial parameters are calibrated.