The Bosphorus Bridge is a major road link between the European and Asian sections of Istanbul. Severely congested traffic conditions are observed on approach roads to the bridge during rush hours, resulting in delays of the order of 60 minutes. Since the number of vehicle lines formed on approach roads is more than the number of available lanes due to the use of shoulders, disorderly flow conditions result. Traffic surveys were carried out to collect speed, flow and concentration data on three approach sections, namely, the last on-ramp before the bridge, and the sections of the main approach road prior to and after the on-ramp. The surveys were carried out in late 1991 before any restrictions were introduced on the use of shoulders, and in 1993 after the shoulders were closed to traffic. Based on these observations, mathematical speed-flow-concentration models were produced for before and after conditions. The data and analyses using these models showed that all three approach sections operated well below their potential capacities. The paper proposes a scheme that could help towards the solution of the problem. (A)
Abstract