Because of heavy traffic on urban expressways, the exits of expressway interchanges have become accident-prone sites. This study explores the impacts of various traffic control devices and road conditions on road safety at interchange exits based on driving behavior data from navigation software. The traffic order index (TOI) based on driving behavior and speed variation is used to evaluate road safety. The general safety characteristics and partitioned safety characteristics of interchange exit sections for different traffic control devices and under different road conditions were described, and a structural equation model (SEM) was constructed to observe the influences of the traffic control devices, road conditions, congestion degree, and time on road safety. The results show that traffic control devices (the number of warning signs, number of advance exit signs and complexity of diagrammatic guide signs) and road conditions (the number of lanes and merging conflicts within 500 m) have significant influences on the road safety of interchange exits. Road conditions have the greatest impact on the safety of interchange exits, followed by the congestion index, traffic control devices, and time. The results could help traffic management departments reconstruct or rehabilitate traffic control devices and enable reasonable road planning at interchange exits. The safety evaluation method for traffic control devices and road conditions based on driving behavior data collected from navigation software could be further used on other roads.

ObjectivesWith the rapid development of expressways in the mountainous regions of southwestern China, closely spaced tunnel-interchange structures have inevitably emerged due to topographical constraints and environmental limitations. Given the unfavorable road geometry and rapid cross-section transitions, drivers face significant safety concerns. This study aims to investigate drivers' safety performance at closely spaced tunnel-interchange sections and determine how safety risks can be mitigated through improved traffic control devices design.MethodsThirty-nine participants conducted an experimental study in a fixed-base simulator. The test scenario was modeled on the Xingyan Freeway-S3801 and accurately reproduced in the simulator. For each safety performance metric, the driving simulator experiments yielded a dataset with 780 observations. To address the idiosyncratic variation due to individual driver differences, a series of linear mixed effects models (LMM) were developed to analyze drivers' behavior responses.ResultsIn closely spaced tunnel-interchange sections, a general impairment of both longitudinal and lateral performance was observed. This study identified potential critical impact variables in traffic control device systems. According to the LMM results: (a) Removing the 0.5 km interchange ramp exit advance guide sign located in the tunnel exit area reduces dangerous behavior in the corresponding impact area. (b) Replacing the 0.5 km interchange ramp exit advance guide sign with arrow pavement markers as an information source supports improved driver performance, promoting driver safety. (c) Adding tunnel exit distance signs within tunnels is recommended to enhance situation awareness for drivers.ConclusionsThis study addresses the scientific issues related to traffic control devices setup for closely spaced tunnel-interchange sections, focusing on identifying potential critical impact variables. The findings provide guidance on the design of traffic control devices for such sections and support revisions to national engineering standards.

The airport road traffic sign system is essential for drivers to find their destinations. However, no comprehensive design standards have been established for airport roadway traffic signs in China. An airport roadway traffic sign system was designed based on the Chinese Road Traffic Signs and Markings standard (GB5768-2009), called scheme 1. A second sign system was established using international standards and following drivers’ recognition, sign information hierarchy, called scheme 2. The Airport Roadway Traffic Sign System Evaluation Method (ARTSSEM) was established to evaluate the effectiveness of the airport roadway traffic sign system. This method includes a goal layer, a method layer, an indicator layer, and a comprehensive evaluation layer. We obtained drivers’ driving behavior data from the driving simulation. The subjects drove at a lower and more stable average speed in scheme 2 (63.71 ± 3.91) than in scheme 1 (65.89 ± 4.81). An ergonomic model that considers the sign system’s information demand, information comprehension, and information volume (DCI) was established and evaluated using subjective experiments. Scheme 2 provided a higher DCI score (0.46) than scheme 1 (0.17). The performance of the sign systems was comprehensively evaluated using the fuzzy evaluation method to evaluate the driving behavior, wayfinding performance, and ergonomics of the sign system. Scheme 2 (76.13) had a higher score than scheme 1 (74.13). The results revealed that scheme 2 performed better than scheme 1. The effectiveness of ARTSSEM was verified by the case study of the Daxing Airport signage system. This study provides a general approach to designing and evaluating other sign systems.