If you ever drive a car in Shanghai, you will very quickly learn a new way to interpret a yellow traffic light.

If you do what you would have done in, say, Hong Kong, and slow down in preparation for stopping at a yellow, you'd be quickly and noisily reminded by the drivers in the cars behind that you had committed a cardinal sin.

For irrespective of what they were taught in driving schools, mainland drivers are apt to regard a yellow light as a signal for them to floor the accelerator to charge across the line before the lights turn red. This results in frequent logjams at busy intersections as cars clog the flow of traffic from all directions. This apparently prompted the government to do the sensible thing in traffic management and introduce a heavy penalty, including fines and a point deduction for those drivers that run a yellow light.