This paper describes the development and application of an analytical procedure for priority entry control strategies at freeway ramps. Vehicles arriving at an on-ramp with different occupancies will be differentiated, and those vehicles with higher occupancies will be given priority entry onto the freeway proper. The objective of the priority-control strategy can be to maximize either the number of persons served or the number of passenger-miles travelled, with a primary constraint that the demand for each freeway section will not exceed the capacity of that freeway section. Additional constraints can be specified, such as maximum and minimum metering rates, etc. The analytical procedure encompasses two models. The first is a simulation model which is deterministic and macroscopic, and predicts the freeway traffic performance as a function of freeway design and allowable ramp inflows. The second is a decision model which has a linear programming formulation and selects a control strategy which meets the above objectives and constraints. The simulation model has been validated under field conditions, and the predicted traffic performance compares very favorably to actual, measured traffic performance. The two models have been integrated and computerized, and the composite model has been applied to the east bayshore freeway in the san francisco bay area to demonstrate its application and to provide the california division of highways with results which may be considered for possible implementation. A series of investigations were undertaken with the computerized model to determine the sensitivity of the overall measures of effectiveness to practical considerations of constraints, and to consider the consequences of such control strategies on changing the traffic demand pattern. (a) for the covering abstract of the symposium please see irrd abstract no. 224453.
Abstract