关键词: 交通工程, 换道风险评估, 换道时空风险指数, 高速公路出口衔接城市路段, 风险等级评定

Abstract: To accurately identify and assess the traffic risk of urban road sections connected to freeway exits, this paper proposes a lane-changing spatial-temporal risk index TRCI (Transitive Risk Coupling Index) that integrates risk proximity level (RNL) and risk severity level (RSL). First, vehicle trajectory data are used to analyze the trajectory characteristics of lane-changing vehicles on road segments, lane-changing positional properties and lane-changing influencing factors. The results show that the relative position of vehicle lane-changing is concentrated in the intervals of 0.1 to 0.2 and 0.4 to 0.6. The lane-changing collision time (LCTTC) is introduced and integrated to the MTC(Margin to Collision) to get the RNL and RSL to characterize the spatial temporal risk characteristics of lane-changing. The Deng's grey correlation method is used to obtain the spatial-temporal risk index of lane-changing (TRCI). The cumulative frequency method is used to determine the thresholds for serious, serious, general, and minor conflicts, respectively. The cumulative frequency method is used to determine the thresholds of serious, more serious, general and minor conflicts as 0.30, 0.51 and 0.67 respectively, and comparing TRCI with TTC and GAP for the identification of the risk of lane-changing conflicts. The freeway exits connecting with the urban road sections are divided into 32 segments and 128 blocks, and lane-changing conflicts are analyzed in terms of their distributional characteristics and risk level assessment. The results show that the effective identification rate of the risk of vehicle lane-changing spatio-temporal risk index TRCI is improved by 85.10% on average compared with that of TTC, and 49.75% on average compared with that of GAP. The performance of the vehicle lane change conflict severity prediction model constructed based on the XGBoost algorithm for freeway exits bridging urban roadway segments performs better than traditional methods. The F1 scores are improved by respectively 11.28% and 1.40% compared with the GBDT(Gradient Boosting Decision Tree) and RF(Random Forest) models. The conflict points in the study section are most intensive in the sections of 3 to 5, 14 to 18 and 21 to 23. The sections of 4 to 5 and 15 to 18 are in high-risk status, which indicates that the exit ramps, guided lanes and surface roadway merging points are the areas with the highest risk of lane change conflicts. The study provides theoretical support for the analysis and management of traffic safety in the urban road section connected with the freeway exit.

Key words: traffic engineering, lane change risk assessment, transitive risk coupling index, freeway exits connecting to urban roadway segments, risk level assessment