Freeway access management activities have traditionally taken a nominal approach to safety. Acceptable safety performance is presumed to result from attaining some desired interchange or ramp spacing. This approach oversimplifies driver behavior and complex interactions between roadway geometrics, traffic operations, and safety. The objective of this paper is to quantify the relationship between ramp spacing and freeway safety, with safety defined as number of accidents, or accident consequences, by kind and severity, expected to occur during a specified time period.
- Review origin of current guidelines for access separation from interchange ramps
- Review recent Virginia study on the relationship between access spacing from interchange ramps and crash rates
- Suggest new standards for the optimum access point spacing
Findings and Recommendations: Access Spacing from Interchange Ramp
These guidelines do not establish ramp and interchange spacing standards. Rather they provide a process and criteria for assessing spacing in a given context to assist planners and designers in considering the feasibility of new or rebuilt interchanges and ramps. Interchange spacing is defined as the distance between the centerlines of successive crossroads with interchanges on a freeway.