A Queuing and Statistical Analysis of Freeway Bottleneck Formation

A modified approach to treat traffic flow parameters (flow, density and speed) has been introduced in this paper. A queuing analysis has been conducted on traffic flow data on Interstate 94 in the Minneapolis-St. Paul metro area. A methodology has been developed to calibrate loop detector count data. Corrected flow data has been subjected to analysis using queuing analysis to compute densities and speeds on freeway sections. Statistical analysis identifies 'active bottleneck' locations on freeways and sections where bottlenecks occur because of disturbances caused by downstream bottlenecks propagating backwards in the form of shockwaves. A sample of six days on Interstate 94 was considered for the analysis. Our analysis reveals that the same section cannot always be characterized as a 'bottleneck' location; at some times it is active and at others, it is subject to downstream bottlenecks. Traffic flow characteristics change and that leads to changing situations on each freeway section.