Evaluation of tunnel retro-reflective arch in an extra-long tunnel based on the matter-element extension method.

Traffic safety devices are one of the most important tools used to improve safety in tunnels. The tunnel retro-reflective arch (TA) plays a crucial role in stimulating drivers, relieving visual stress, and improving safety. However, determining the TA spacing mostly relies on experience and relevant standards are lacking. The aim of this research was to evaluate the degree of influence of the TA on driver behavior, visual aspects, and psychology in different zones (overall tunnel, curved segment, and middle segment) of extra-long tunnels. To test the influence of TAs, four scenarios were constructed, including three alternatives with different TA spacings (200, 300, and 400 m), and one no-arch design as a control alternative. Based on a driving simulator, the evaluation indicators related to driving safety, smoothness, and handling stability were selected and analyzed. We acquired data every 50 m as an analytical unit. The results show that the TA significantly affects driver behavior, visual aspects, and psychology. According to the matter-element model result, setting the TA spacing to 300 m in curved segment and in the tunnel overall is the best option. In the middle segment, the setting spacing of 400 m is ideal.