Schiphol tunnel

In 1966, near Amsterdam's airport Schiphol, a tunnel was opened. In the years that followed, the tunnel turned out to be very accident prone --- to the extent that an ambulance had to stand by 24 hours a day. Having an accident in the tunnel was said to be the fastest way to get to downtown Amsterdam .....

In the 1980s, the tunnel was reconstructed, following the advice by vision experts Leeuwenberg and Boselie (Radboud University Nijmegen) --- the result: no more accidents. See the story below for more details about the main visual factor that caused the accidents.




On request of the Department of Traffic, Leeuwenberg and Boselie looked into the problem, and found a dozen factors that made the entrance of the tunnel visually turbulent. The main cause of the accidents was the following factor that perfectly illustrates the role of simplicity in vision.

When car drivers approached and entered the tunnel, they thought the tunnel entrance was rectangular (see next figure). From their viewpoint, this was the simplest interpretation --- be it correct or incorrect (how do you see it in the picture above?).


Then, while going in deeper,  .......


....... they got the impression they approached the end of the entrance much faster than they had anticipated.

What they did not realize, however, was that the end of the entrance was actually much closer by than their simplest interpretation suggested --- because the actual shape of the entrance was non-rectangular as in the next figure.


Unaware of this actual shape, the drivers thought they approached the end of a rectangular entrance so fast because their car was going faster and faster --- as if they were sucked in. Therefore, they hit the brakes, thus causing chain collisions.


As said, Leeuwenberg and Boselie advised a reconstruction, after which such accidents were history.

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