Abstract
In 1978 the city of Leiden introduced the so-called 'ofos'. This Dutch acronym stands for ‘blown-up cycle lane'. It boils down to the provision of a second stop-line, some 4 to 6 meters before the standard one. When the traffic light shows red, car drivers have to wait behind this second stop-line while cyclist can overtake them at the right hand side to reach the ofos in front of the first car. Thus the ofos has the width of the whole lane between the road axis and the curb. When the light changes to green the cyclists start first, those turning left not conflicting with car traffic moving straight on. Weaving manoeuvres are strongly reduced in number.