Impact of Highway Traffic Incident on Speed Based on ETC Data: A Case Under Different Traffic State

Highway traffic incident is an important aspect of traffic safety and congestion management, generating negative impact on traffic flow. However, traffic parameters change under different traffic states after incident are not clear. Therefore, the study proposes a speed impact extent analysis method based on highway incident information and electronic toll collection (ETC) system data, exploring speed impact extent after incidents on highway traffic state. We crawled incident information through the Sichuan Highway online platform, combined with ETC gantry data to study the speed impact extent after incidents. Taking incidents occurrence time as nodes, trends of speed change are studied at an interval of 0.5 h between 1.5 h before and 4 h after, divided according to different traffic states. Then, Speed Impact Index (SII) is constructed to quantify speed impact extent after incidents. The results show that SII could effectively reflect speed impact characteristics after incident. We found when traffic state is congested-flow, speed impact is most significant (there is also a significant increase in speed) after incident. In addition, vehicle rear-end has the highest frequency among all types of incidents, which has a significant impact on speed. Vehicle rollover and spontaneous combustion also have significant effects on speed.