The safety effect of traffic signs for median openings on one-side-widened freeways

Abstract

Aging infrastructure requires timely maintenance, expansions and upgrades. Due to limited project budgets, particularly in low- and middle-income countries, highways are sometimes widened on only one side, and openings are configured on existing medians, rather than existing medians being removed altogether. The potential safety risks associated with this uncommon road configuration call for extra attention when designing, laying out and placing traffic signs around median openings. Thus, this study aims to develop a thorough understanding of sign configuration to improve the safety of median openings. A section of the Binlai Freeway in Shandong, China, was selected as the study site. Driving simulation experiments were carried out to test the safety performance of different sign configuration plans, which were combinations of signage for lane-specific speed limit and recommended vehicle type, no lane-changing and impending median opening warning. The data collected from 30 drivers across four driving sessions determined the safety benefits brought by different signs through lane changing maneuvers, speed control, surrogate safety measures and subjective perception measures. The one-way repeated measures Analysis of Variance (ANOVA) and Generalized Estimating Equations (GEE) were applied to identify the effect of the guide signs during the four simulated scenarios. The GEE modelling results show that for one-side-widened highways, additional signage for lane-specific speed limit and recommended vehicle type is recommended to implement around median openings. The findings from this study can effectively inform open-median traffic control on one-side-widened highways.