An Evaluation of the Interior Design of the Stockholm Bypass Tunnel – A Driving Simulator Study

Maintaining high levels of road traffic safety is always important and when the road is in a tunnel, and especially in a long tunnel, maintaining the highest possible level of safety is paramount. In Sweden, the Stockholm bypass tunnel has been scheduled to commence construction in 2013. The tunnel will be approximately 18 km in length. The length of the tunnel is expected to affect the drivers’ experiences pertaining drowsiness, arousal, distraction and feelings of safety and security. The study included 24 participants, 12 men and 12 women, aged 30-45. All of the participants drove two versions of the tunnel, one version with a decoration design in terms of string lighting in the ceiling of the tunnel and one version of the tunnel without any decoration design. Eye tracking behaviour was measured during the study. CR10 ratings of four subjective dimensions (distraction, visually cluttered, visually stimulating/arousal and safety and well-being) during the drive were also measured. The results revealed that 58 per cent of the participants preferred the tunnel with the strings of light in the ceiling and 29 per cent preferred the tunnel without the ceiling lighting. 13 per cent prefer neither one design more than the other. The participants perceived feelings of their driving through the tunnel suggested that the tunnel with the ceiling light design was experienced as being more ”visually cluttered” than the tunnel without the light strings but at the same time it was also experienced as more ”arousing/stimulating”. Mean glance duration times suggested that although there was a significant main effect of the tunnel with the string lighting and in specific areas of the tunnel, the drivers were looking at the ceiling lighting but using short glances (445.3 ms with lighting and 234.3 ms without lighting). The negative safety implications of the elaborate interior lighting features would appear to be minimal in terms of distraction and irritation whereas the safety benefits in this particularly long road tunnel, in terms of subjective feelings of visual stimulation is encouraging. Based on the participants’ experiences of the interior design concept of the 18 km long tunnel, having stimulating lighting features in different locations alone the length of the tunnel is recommended.