Modeling Freeway Traffic Flow under off-Ramp Congestion

This paper studies the effects ofqueue formation in the bottlenecks at off-ramps on thecapacity of the freeways. six expressway exit-ramps throughout the city of tehran, iran wereselected and their traffic flows were observed in thirty-minute intervals during which the queueformation and queue elimination occurred. assuming that in the absence ofthe queue, the trafficflow is in its normal state, the changes in the volume ofthrough vehicles has been modeled as anaverage estimator ofthe change in the expressway capacity.the developedmodelsprovethatthechanges infreeway capacityaredue to queueformation attheoff-ramp sections. however, the estimatedfigures are differentfrom those obtainedfrom the theoryoffreeway capacity. the conclusion is that lane blockage is only one ofmanyfactors that affect thefreeway capacity while the queue forms. since it is' not possible to quantify all those factorsindividually, the resulting models are macroscopic estimates ofthe phenomenon.