Safety Concerns Regarding Merging in Tunnels – A Simulator Study

Abstract

The Stockholm bypass project is by far the largest road/tunnel project ever undertaken in Sweden and has been scheduled to commence construction in mid-2014. The tunnel will be over 16 km in length with two parallel tunnel tubes containing a three lane motorway. In the present study a 3D model of the Stockholm bypass tunnel has been constructed for the purpose of visualizing and further testing traffic safety and traffic management issues related to ramps exiting and entering a tunnel. Twenty-three participants with a mean age of 33.7 (SD 11.8) years drove the MUARC advanced driving simulator in two different environmental conditions (tunnel and freeway) and two different speed conditions (80 and 100 km/h). Various traffic scenarios included interaction with surrounding and merging vehicles in a comparison between the tunnel and freeway environments. Dependent measures of driving performance included vehicle speed, speed variability, lane position, lane position variability, lane excursions and time to headway. Furthermore, eye tracking and subjective measures of driver workload were used to compare participant’s reactions across environments. Results suggest that when sight lines were not restricted on the freeway, drivers reduced speed during the first merge event only. For the tunnel and freeway with restricted sight lines, there were no significant differences in mean speed across the merge segments, although even in these environments there was a trend for drivers to reduce speed at the first on-ramp. Overall, it appears that driving environment and the restricted sight lines played a limited role in drivers’ behavioural response to the merging vehicles.

Keywords: Stockholm bypass, driving simulator, tunnel design, restricted sightline, merging zones, traffic scenarios, driving performance, lane excursions, eye tracking, NASA-RTLX.

DOI: 10.54941/ahfe100627