The Relationship between Ramp Length and Traffic Flow Speed (TFS) for Interchange

The relationship between ramp length and traffic flow speed (TFS) was studied based on analyzing the design elements of geometry alignment for interchange. After analyzing the process of vehicle running in the ramp, the speed change process was divided into four forms, namely, one deceleration and acceleration process, one deceleration process, one acceleration process and more than one deceleration and acceleration process, and then the relationship between the ramp length and TFS was established respectively. Through an example of the HeDa Interchange of Heilongjiang Province, it showed that although the differences of alignment units of ramps can result in various speeds and specific expressions of relationship between ramp length and TFS. However, all of these relations can be expressed by homologous nonlinear function.