Driver Behavior on Speed-Change Lanes at Freeway Ramp Terminals

Abstract

Speed-change lanes (SCLs) at freeway ramp terminals are critical elements in freeway design, as they provide the necessary access between the freeway and the adjacent local street network. Prevailing guidelines for the design of SCLs are well established and based on long-standing research about the performance characteristics of vehicles and principles of geometric design. Little is known, however, about the behavior of drivers who are making freeway entry or exit maneuvers. An NCHRP project is tasked with reviewing existing design guidelines and practices, as well as modern driver behavior and vehicle performance, to develop improved design guidance for freeway ramp terminals. This paper discusses findings from the driver behavior study of the project, which indicate that the SCL lengths on entrance ramps recommended by current guidelines are sufficient for subject drivers' typical merging maneuvers under low to moderate congestion and that exit ramps most appropriate for subject drivers may be longer than recommended by current design guidelines.