What is it about?
The present study aims to investigate the crash characteristics analysis of the expressway long tunnels by proposing a novel zoning approach. Based on the findings of the study, various countermeasures to improve the traffic safety in long tunnels are reccomended.
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Why is it important?
Tunnels, as a part of expressway network, play an important role in improving the alignment standards, reduce travel time and protect ecological environment. However, due to its semi-enclosed space structure, the driving environment in the tunnels is diﬀerent from that of the open road sections. Another eﬀect is the drastic changes in the visual environment at the tunnel entrance and exit that might induce temporary ocular blindness. In addition, due to limited inner space, collisions in the tunnel are often more diﬃcult to rescue, resulting in crashes with wide impacts, and with a high probability of secondary crashes. Therefore, an in-depth research on tunnel is of crucial importance and urgently needed.
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This page is a summary of: Crash analysis of expressway long tunnels using a seven-zone analytic approach, Journal of Transportation Safety & Security, June 2019, Taylor & Francis, DOI: 10.1080/19439962.2019.1605642.
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Crash analysis of expressway long tunnels using a seven-zone analytic approach
Research efforts have been made to understand tunnels’ traffic safety. Most of the previous studies have not considered the different features of tunnels with different ranges of length comprehensively. Generally, three- or four-zone approach has been adopted, with which the entrance and exit parts of a tunnel are considered symmetrical in the safety analysis. This study employs a seven-zone analytic approach for the safety investigation of 18 expressway tunnels with length ranging from 2 to 3 km. The results reveal that the crash rate increases firstly for the entrance zone, then decreases for the midzone and again increases at the exit zone. The high crash rates at the access, entrance, and transition zones are attributed to rear-end crashes. Although single-vehicle crashes take place in the mid and exit zones (1) at the tunnel entrance: failure to maintain safe distance; (2) in the midarea: failure to maintain safe distance, fatigue driving, overspeeding, and improper lane change; and (3) at the tunnel exit: overspeeding and improper lane change mainly contribute to the crash occurrence. Friedman test was performed to test the significance of the contributing factors. The crash occurrence mechanism is discussed for the selected long tunnels. Finally, engineering and policy countermeasures are recommended to improve traffic safety in expressway tunnels.
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