Study on optimization design of guide signs in dense interchange sections of eight-lane freeway

The eight-lane freeway resulting from reconstruction and expansion typically exhibits short distances between interchanges and a wide road section. Nonetheless, the absence of specific guidelines for the placement of guide signs in dense interchange sections of the eight-lane freeway results in inadequate design, thereby impeding drivers' ability to read and comprehend the signs. To tackle this issue, the study employs two interchanges 2.48 km apart on the Jinan-Qingdao Freeway as a case study. Four optimization schemes for guide signs are developed based on drivers' information requirements and compared with the current guide sign design scheme. Thirty-nine drivers were recruited to gather detailed driving behavior indicators via a driving simulation experiment. The impact of the guide sign optimization scheme on driving behavior is analyzed, and the overall effects are evaluated using the non-integer rank RSR method. This study aims to identify an optimal approach to guide sign design for dense interchange sections. The results indicate that the impact of guide signs in dense interchange sections on drivers is primarily concentrated between the two interchanges. Specifically, the addition of a 2.5 km exit advance sign enhances drivers' speed regulation level, the inclusion of navigation voice improves operational stability, and the presence of pavement words at exit diversion locations enhances psychological comfort for drivers. By considering the comprehensive effectiveness of each optimization scheme, it is evident that schemes 5 and 2 exhibit superior optimization effects. This suggests that providing advanced notice of exit information in dense interchange sections of eight-lane freeways is an effective measure to enhance freeway service levels and ensure driving safety. It is recommended that under the conditions of insufficient interchange spacing, the information of interchange exits should be forewarned in advance. Additionally, auxiliary navigation voice and pavement words should be employed to enhance drivers' information perception levels, thereby mitigating the risk of missing exits due to limited reaction time. This paper serves as a significant reference for informing the optimal configuration of guide signs, thereby contributing to the meticulous development of standardized specifications.