Investigating the self-explaining performance of visual guidance facilities in extra-long spiral tunnels based on drivers' spatial perception and visual attention distribution.

Enhancing the weak visual reference system is crucial for improving drivers' spatial perception in extra-long spiral tunnels, which require continuous turns and uphill/downhill maneuvers. Using the Midicun Tunnel as a prototype, we tested three common visual guidance facilities-horizontal stripes, retroreflective rings, and edge markers-by constructing scenarios with each facility individually and in combinations of these facilities. A comprehensive indicator framework was developed to assess the impact of these facilities on drivers' spatial perception and attention distribution. The self-explaining performance of each facility was evaluated using the matter-element model combined with the entropy weight method. Additionally, drivers' subjective acceptance of each facility was measured using the Technology Acceptance Model (TAM), which offered insights into their internal expectations and cognitive state. The results reveal that drivers tend to drive close to the inside wall of the curve in the continuous curved section of a spiral tunnel. Installing edge markers improves the self-explaining performance of the tunnel's horizontal right-of-way, increasing the distance between the vehicle and the tunnel wall. Installing the retroreflective ring guides drivers' attention to the central area ahead, enhancing the longitudinal right-of-way. However, when used alone, it can lead to longer fixation durations and lower saccade frequencies, an issue that can be mitigated by combining them with other features. Comprehensive evaluations and subjective acceptance surveys indicate that scenarios with multiple facilities provide optimal self-explaining performance and best meet drivers' psychological expectations. Among individual installations, edge markers are the most effective, followed by retroreflective rings, with horizontal stripes showing the weakest performance. Based on these findings, specific recommendations for optimizing visual guidance in spiral tunnels are provided, offering valuable insights for improving tunnel environments.