Norwegian road tunnels: Ventilation, pollution and pollution distribution

To reduce the drivers feelings of fear and unpleasantness in road tunnels increased ventilation with the use of visibility meters and electrostatic precipitators, lighting and maintenance works are mentioned as solutions. A parallel control of road tunnel ventilation based on CO and visibility as equally valuable control parameters can reduce the discomfort due to reduced visibility during winter seasons. The use of electrostatic precipitators can not alone increase visibility, regular cleaning of the road tunnel must be carried out if the visibility should be maintained for driving comfort. Painting the side walls of the tunnel have no long time effect on the visibility in road tunnels.