An aerial traffic survey and data reduction system was developed for the purpose to obtain continuous traffic data on the spacing of vehicles, speed, density, volume, acceleration and deceleration, lane changes and the general behavior of vehicles on two urban freeways in columbus, ohio. These data were evaluated with regard to real world safety conditions in the car following, the propagation of disturbances, the stability and the quality of traffic flow. The most important discoveries made were the multilinear speed-density relationships and the hysteresis phenomenon of traffic flow which shows the changing characteristics of traffic flow during the build up phase and the recovery phase of a kinematic disturbance. The new knowledge derived from aerial surveys and the research on traffic dynamics was applied to a ramp metering system for southbound morning peak traffic on 171 and to the development of a loop detector for density and speed measurements. Finally a cost analysis of the aerial survey method was carried out to explore practical applications for freeway operation and control. (Author/publisher)
Abstract