Research On The Operating Characteristics Of Two-lane Highway Tunnel In Mountainous Area

In recent years,the construction of highway tunnels has increased year by year,and the accident rate and accident severity of tunnel sections are significantly higher than those of general sections,and tunnel traffic safety is always a high concern for many scholars.However,most of the studies on tunnel safety have been focused on highways and urban roads,but less on mountainous low-grade highway tunnels,which are more complex in terms of road environment and traffic composition than highways.The discovery and elimination of safety hazards in low-grade highway tunnels is extremely important to promote the development of low-grade highways with high quality.Considering the complexity of the mountainous two-lane highway tunnel environment,this paper builds a real-world driving test platform for mountainous highway tunnels and selects nine single-hole two-lane tunnels in both directions,including four short tunnels,three medium-length tunnels and two long tunnels,in the Pengshui County section of National Highway G211 in Chongqing.The driving behavior and physiological index parameters,such as driving speed,acceleration,driver heart rate,etc.,were collected from 20 subject drivers through the tunnels.The main findings are as follows.(1)Combined with the actual driving environment of the tunnel section,we analyzed the vehicle running speed change characteristics of the tunnel section,and found that the small radius circular curve has a strong constraint on the running speed of the short tunnel,and the speed change is smaller when the line of the entry and exit units is straight;the deceleration behavior is more obvious before the entrance of the medium and long tunnels due to the illumination;there is a certain acceleration behavior when the road line of the entry and exit units of the long tunnels is better.Different drivers’ driving behaviors inside the tunnels are different,and the speed dispersion is more varied,but overall the speed dispersion is the smallest in short tunnels,followed by medium-length tunnels,and the largest in long tunnels.(2)The differences in steady speed following behavior between medium and long tunnels were compared and analyzed,and correlations were made between following distance and following speed,following distance and relative speed,and following time distance and following speed.The results showed that the following distance and following speed were positively correlated,and the following speed in medium and long tunnels was greater than that in long tunnels with the same following distance;the fluctuation range of relative speed increased gradually with the increasing following distance;the following time distance and following speed in medium and long tunnels had no obvious regularity,and the following time distance in long tunnels showed a trend of decreasing and then increasing with the increasing following speed.(3)The relationship between the longitudinal deceleration and the heart rate growth rate of drivers was investigated by using the heart rate growth rate index,which showed that there were some differences in the distribution of the peak heart rate points in the tunnel entrance and exit units,and the heart rate growth rate of the medium-length tunnel entrance unit was higher than that of the long tunnel entrance unit,while the heart rate growth rate of the medium-length tunnel exit unit was lower than that of the long tunnel exit unit.The heart rate growth rate of the medium-length tunnel inlet cell is higher than that of the long tunnel inlet cell.Meanwhile,there is a strong positive correlation between the longitudinal deceleration rate and the heart rate growth rate of the inlet and outlet units.This study provides theoretical support for the study of driving load in mountainous two-lane highway tunnels.