Design and evaluation of visual guiding facilities along urban road tunnel horizontal curves based on vision and speed perception

With continuous increase in the number and length of urban road tunnels, traffic safety in the road tunnels has attracted ever greater attention. In particular, driver's sight distance and sight zone along urban tunnel curves are constrained, and potential safety hazards are prominent. Herein, from the perspectives of active guidance, using visual guiding facilities to enable drivers to accurately perceive the orientation of the tunnel curve alignment and to control the speed reasonably have become a key research point with theoretical significance and practical application value. In this study, four types of schemes for urban road tunnel horizontal curves were constructed and evaluated by simulation experiments. Scene a was a rare scene without any visual guiding facility in practice, ordinary Scene b was a common scene in an urban road tunnel, Scene c included chevron alignment signs (additional to Scene b), and Scene d included LED arches (additional to Scene b). Glance location occupancy, mean glance duration, accuracy of speed perception and reaction time were used as driver performance indicators, in which the four types of scenes were analyzed and evaluated by visual test, speed perception test and subjective evaluation. The results showed that compared with Scenes a and b, Scene c with chevron alignment signs can improve alignment guidance along road tunnel horizontal curve, while the test results of Scene d with LED arches as proposed in this study had the best performance in all aspects. The research scheme and test results can provide reference for visual guiding facility design and traffic safety improvement along urban road tunnel horizontal curves.