The tunnels will be designed for a safe journey, where an aesthetic design programme aims to prevent accidents.
The design principle of the aesthetic design programme is based on knowledge of human behavior in tunnels. Good ease of orientation is an important aspect that influences the design. Clear information about where one is in the tunnel system is also essential to the sense of safety.
Aesthetic design programme and driving experience
The tunnel’s aesthetic design consists of for example artistic lighting, unique artwork associated with each traffic interchange and markers, or indicators, describing how far the road users have travelled in the tunnel.
The aesthetic design programme has been evaluated through an in-depth Human Factor study, including a driving simulator in cooperation with VTI, the Swedish National Road and Transport Research Institute. The study aimed to describe how human behavior is affected by a complex traffic system, and to examine how the normal driving experience is affected by the aesthetic design programme. Driving aspects that have been evaluated include visual distraction, lateral deviation (does the driver stay in the middle lane), average speed and differences in speed (are there any sudden speed changes), steering wheel movements and braking behaviour.
Experiences from occurred vehicle fires in the tunnel Södra länken show that the behaviour of road users during an accident is hard to predict. The basic idea of the safety concept in Södra länken is similar to the Stockholm bypass, i.e. road users upstream of a fire should evacuate by foot, via escape routes, to a parallel tunnel tube. However, there have been a few cases where road users have been seated in their cars in a smoke free environment upstream of a fire, and despite this decided to leave the smoke free environment and drive into a smoke-filled tunnel section. This is a risky behaviour since conditions downstream are unknown and potentially dangerous should the fire grow large. There could be various reasons for this; the road users have not seen, heard or understood the evacuation message, they have understood but chosen to ignore the evacuation message since they are determined to fulfill the original purpose of their journey, e.g. to get home.
The project aims to further investigate this situation, e.g. with the help of a driving simulator. In these studies, a test person would drive along the tunnel and suddenly reach an accident, e.g. a burning vehicle, partly blocking the road. The test person would still have the choice to drive past the accident into a smoke-filled environment. The aim of the study would be to investigate how people react to the situation of a burning vehicle partly blocking the road, and why they act one way or another. Step two would be to investigate how people actually react once they have driven into the smoke-filled environment where visibility is low and orientation difficult. Results from the study could be used to determine if any channels for communicating evacuation messages need to be improved or if any new channels are required.