Central Avenue is a long straight road, several kilometres long. Both my home and my office are on Central Avenue, and the diagram below shows their positions, together with two sets of traffic lights that lie in between. [image of diagram] Both sets of lights turn to green for Central Avenue traffic simultaneously, showing green for exactly two minutes, turning green again exactly two minutes later. I cycle to work every morning at a steady speed of 5 metres per second (except, of course, whilst waiting at traffic lights).