Study On Driver’s Mental Workload And Safety Risks Of High-Density Interchanges

In recent years,the density and complexity of the expressway network have gradually increased,and the spacing between adjacent interchanges has become smaller.It is increasingly common that the spacing of more than two consecutive interchanges does not meet the requirements of the current technical standards,resulting in highdensity interchanges.As an essential component of the interchange layout,the length of interchange spacing directly affects the safe operation of the road section and the overall function of the entire road network.Smaller interchange spacing can result in a shorter weaving area between interchanges.Drivers are required to complete operations such as diverging,merging,and changing lanes within a narrow space.It leads to increased driving difficulty and higher mental load for the driver,which can easily cause the driver’s driving ability to meet the driving workload requirements,resulting in mishandling and theoretically increasing the risk of driving.Therefore,it is essential to clarify drivers’ mental load and safety risks in high-density interchange scenarios for safe operation and accident prevention of high-density interchanges.For this reason,this study selected a high-density interchange cluster in the Chongqing section of the G50 Shanghai-Chongqing Expressway to conduct a real-world driving test of minibusses.Under reasonable weather conditions,Physio LAB and Speedbox instruments were used to collect drivers’ ECG data and driving behavior parameters while driving under actual interchange conditions.First,this study analyzed the characteristics of drivers’ heart rate(HR)and heart rate variability(HRV)indicators.On this basis,a model of drivers’ mental workload was developed using factor analysis.The effects of interchange spacing,driving style,gender,and lane change form on mental workload were investigated.The results show that the driver’s mental workload in small-spacing interchanges is higher than in normal-spacing interchanges.Angry drivers’ mental workload is higher than anxious and risky drivers.Female drivers’ mental workload is significantly higher than that of male drivers.The average mental workload of drivers entering the mainline from the ramp(merging)process increases by 13.89% compared to entering the ramp from the mainline(diverging)process.Then,this study analyzed the variation of the driver’s heart rate increase(HRI)in four driving conditions(ramp → mainline,mainline → ramp,mainline driving,auxiliary driving)in the small-spacing interchanges.It is found that drivers’ HRI variation presents four patterns: "convex curve and continuously increasing," etc.The drivers’ HRI increases significantly in the first 50% of the weaving area in four driving conditions,indicating that vehicle weaving greatly influences drivers’ mental workload.Based on the speed and HRI variation regularity,the influenced area of small-spacing interchanges can be defined as the 200 m before the merging point of the last interchange entrance to the200 m after the diverging point of the following interchange exit.Finally,the driving behavior characteristics and their effects on the driver’s mental workload were analyzed with vehicle speed and lateral/longitudinal acceleration as indicators,and the driving behavior risk was evaluated.On this basis,a comprehensive risk model based on drivers’ mental workload and behavioral risk was developed by the CRITIC method.The results show that the driver’s mental workload correlates with speed and longitudinal acceleration in small-spacing interchanges.The comprehensive driving risk of drivers at the entrance section of small-spacing interchanges is higher than that at the exit section.