Safety Analysis and Countermeasures for System Interchange Operation Based on Geometric Components and Driving Behavior

System interchanges have played an important role in traffic flow transference in Chinese freeway network. With the increase of traffic volume, crashes and congestions intensively occur in early built system interchange. How to evaluate the safety level and take effective countermeasures to promote the operating safety of system interchange will be a long-term and tough task in the next decades. This paper analyzes the geometric components of a system interchange and classifies the typical schemes widely built in China into eight forms. Based on driving behavior analysis, the safety influencing segment of interchange (SISI) is defined as the mainline segment affected by the deployment of interchange, causing the variations of traffic flow characteristic and driving behavior. Based on driver's behavior of mainline and ramp, the geometric organizations of traffic flow are classified into seven types and the safety level of all types is further analyzed. Results are the theoretical foundation and important support for future study on safety evaluation, deployment of traffic signs and markings, safety management in system interchange. Countermeasures that have been taken into practical safety engineering in China is summarized from the aspects of geometric component, behavior management and visibility promotion.