The aim of this study is to develop a microscopic simulation model by considering eight-lane divided urban expressway. For this purpose, the partially access controlled Delhi - Gurgaon Expressway which handles about 220,000 vehicles/day has been considered. From the collected data, speed - flow equations of different vehicle types on eight-lane divided urban expressways have been developed using PARAMICS simulation software. The developed simulation model has replicated the ground conditions realistically with the mean percentage error in speed ranging about 2 to 15% across all vehicle types considering the heterogeneous traffic mix prevalent on Indian urban roads. The study revealed that the roadway capacity of eight-lane divided urban expressways is about 11,435 passenger car units/hour/direction. Further, the formation of virtual lanes by vehicles (that is, formation of eight virtual lanes in just the one direction of eight-lane divided carriageway) has been extensively examined and its impact on roadway capacity has been estimated. It was observed from this study that the roadway capacity of eight-lane divided urban expressways under no virtual lanes condition (that is, traffic plying on the demarcated four lane in one direction of eight-lane divided carriageway) would obviously reduce the roadway capacity by about 15%. At the same time, it is to be noted that though the imposition of restriction on virtual lanes decreases the average free speeds by 7%, it would enhance the safety situation due to less vehicular interactions.
Key words: Free speed, speed-flow equations, roadway capacity, lane change behaviour, urban expressways.
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