Optimal off-ramp terminal locating strategy based on traffic safety and efficiency

Off-ramps are key nodes which connect urban elevated highways and auxiliary roads, and the distance between an off-ramp terminal and an intersection (ORTI-D) relates directly to traffic safety and efficiency. The authors introduced a new off-ramp terminal locating strategy considering traffic safety and efficiency synthetically. After building a basic VISSIM simulation model which included two-lane off-ramp, one-lane auxiliary road before the weaving area and four-lane entrance road before a no-signal intersection, the functional relationships of the LWA (Length of Weaving areas)-TIT (Time integrated time-to-collision) and the LWA-TTD (Total traffic delay) were developed. On this basis, the genetic algorithm was used to obtain the traffic safety-efficiency optimal ORTI-D and a positive correlation between the weaving proportion and the optimal ORTI-D was found. The methods developed in this paper can satisfy the requirements of off-ramps engineering design and contribute to solve traffic safety and efficiency problems in traffic management.