Driving behavior and safety performance in spiral tunnel groups: A naturalistic data analysis

Area of Science:

• Traffic Engineering and Road Safety
• Human Factors in Transportation

Background:

• Understanding naturalistic driving behavior in complex freeway tunnel environments is crucial for enhancing road safety.
• Spiral tunnel groups present unique challenges due to closely-spaced curves and varying gradients.

Purpose of the Study:

• To investigate driving operations and safety performance characteristics in naturalistic driving along freeway spiral tunnels.
• To identify high-risk directions, critical sections, and contributing factors to safety variations in spiral tunnel groups.

Main Methods:

• Thirty-four participants completed 25 km driving runs in both directions of spiral tunnel groups.
• Driving behavior was quantified using speed, acceleration, lateral lane position, and steering parameters.
• A composite safety performance index was constructed using the rank-sum ratio method.

Main Results:

• Driving downhill showed higher speeds, poorer speed consistency, and increased lateral lane dispersion compared to uphill.
• Uphill driving exhibited greater fluctuations in acceleration and deceleration, indicating higher longitudinal control effort.
• Connector tangent sections and tunnel entrance zones demonstrated the poorest safety performance.

Conclusions:

• Safety risk is significantly higher when driving downhill in spiral tunnels, primarily due to grade-driven speed regulation.
• Longitudinal grade is a more dominant factor influencing safety performance than horizontal curve direction.
• Findings support data-driven improvements in geometric design and safety management for spiral tunnel environments.