Lateral positioning behaviour of car drivers near tunnel walls

An experimental programme was exected with the aim of analysing the lateral positioning behaviour of car drivers in the vicinity of tunnel entrances in relation to (changes in) the available lateral distance between the right shoulder line and the right tunnel wall. Two tunnels were selected: 1) the Benelux tunnel with a sudden 3.25 m narrowing due to the wall (4.05 m to 0.80 m) at 100 m before the tunnel entrance, and 2) the Vlake tunnel (control condition) with a constant free lateral distance of 4.05 m. Normal traffic in the right lane was recorded with video equipment during the approach and entrance to the tunnels, and the lateral positions of cars were analysed quantitatively. At the location of the sudden narrowing of the wall at the Benelux tunnel free moving and clustered cars show a mean shift of 0.33 m to the left in relation to their position 100 m before that narrowing. This shift increases further after the narrowing of the wall, reaching a maximum value of 0.70 m just at the location of the well known "black hole" at the tunnel entrance. The shift decreases again after that entrance. No systematic shift in lateral position could be noticed for the cars at the control location of the Vlake tunnel.