Driving characteristics of static obstacle avoidance by drivers in mountain highway tunnels − A lateral safety distance judgement

Static obstacles (tunnel sidewalls, barricades, etc.) on the side of mountainous highways change the spatial range of the road during driving, restricting the driver’s freedom of driving while possibly triggering the driver’s shy away effect, which poses a specific potential safety hazard. To understand the characteristics of driving behaviour in mountain highway tunnels with different tunnel lengths and lateral obstacles, nine tunnels in Chongqing were selected for real-vehicle tests, and data on driving trajectories, speeds and other metrics were collected from 40 drivers. Analyse the driver’s need for lateral safety distance in different scenarios, defines the conditions and scope of the shy away effect, and establishes a multi-scenario “distance-trajectory” offset prediction model to adjust the offset under varying lateral environments by setting different facilities. The results show that drivers exhibit some avoidance behavior towards lateral static obstacles, but the extent of the shy-away effect varies based on tunnel length. By widening the lateral clearance to 0.925 m on the left side and 1.450 m on the right side of the road to meet the driver’s requirements for lateral safety distances, unreasonable avoidance behaviour can be reduced. Combined with the trajectory fluctuation characteristics of drivers in different tunnels, it is proposed to set up the traffic safety facilities in a manner more aligned with driver behavioral habits, with a place set up 110 m before the entrance of the short tunnel, two places set up in the medium tunnel at L/2 − 200 m, L/2 + 100 m (where L is the length of the tunnel), and three places for long tunnels at L/2 − 400 m, L/2 m, and L/2 + 300 m. For extra-long tunnels, facilities are to be set up in cycles of 500 m, 1000 m, and 1500 m intervals. In the cross-section where different drivers are prone to apparent trajectory offsets, a driving behavior prompt sign is added to help correct the driving trajectory.