| Expressways have increasingly become an important channel for dissipating urban traffic congestion and supplying the demand of long-distance commuting,with the rapid growing urban sprawl and traffic demand.It has also made expressway traffic congestion a concern issue of our society.As the junction of mainline and on-ramp,and the difference of roadway facilities and traffic flow characteristics from the basic segment make merging section a significant bottleneck one that usually results in traffic jams during peak hours.Based on measured data,traffic flow features of merge influence area are analyzed in the macroscopic or microscopic level,while the detailed queuing modeling of on-ramp junction bottleneck is proposed.Through the conducted queuing modeling,explores the bottleneck mechanism of the junction area is probed,besides,a method for on-ramp junction bottleneck capacity and level of service is provided.This paper first observes and collects data of several typical urban on-ramp junction in Nanjing.After traffic data extraction,with regard to different types of on-ramp junction,the macroscopic traffic flow spatiotemporal performance and lane-changing behavior during the congestion evolution process are discussed.Combined with empirical data analysis and probability theory,a state-dependent queuing model for merge area is established,moreover,evaluation indicators for the performance of road infrastructure are introduced and the model is validated.Furthermore,the bottleneck mechanism of the merge influence area is explored via the indicators.In the end,an analysis instrument of capacity and quantity of service for onramp merge area is supplied,compared with the existing classic analysis model. |
