There's a curious affliction that affects some drivers - they slow down when they see a green traffic light. More often than not this means you end up missing the green light because by the time you get there, it's gone red. I know some might argue that they're slowing down in case the light goes red, but that's not really a valid argument. That's like saying that it's OK to start driving through a red light in case it's about to go green. The same people also seem to have a problem when the lights do go red though - they begin to slow down way too early. I had this happen to me a couple of weeks ago. We must have been a good 100m from the lights doing all of 20mph (a dawdler) and they changed to red. Instantly, the brake lights on the car in front came on. Ok I expect people to slow down and stop when they see a red light, but not when they're two blocks away from it traveling at a snail's pace. I wondered if he might have read my blog some months ago where I talked about traffic flowing - about being able to modulate your speed on the approach to a junction but then I remembered that I did not write "jam on the brakes as hard as possible the instant the lights go red".
I think part of the problem is that around here (Utah), a great many people actually drive with their left foot on the brake pedal all the time. It's led to a 'cry wolf' driving situation where a lot of drivers just don't respond to brake lights any more because in a lot of cases they don't mean anything. I've followed people down residential streets and along motorways with their brake lights going on and off at random intervals whilst they weren't slowing down. It's because the brake light switch responds to the slightest pressure on the pedal - the weight of the driver's foot is enough to do it, even though it's not enough to apply the brakes. Now I know from talking to a few drivers who do this that they are under the impression that it makes them a safer driver. Far from it - in fact it makes them one of the most dangerous drivers on the road. They're uncoordinated because they're using two feet, and they create a situation where the traffic behind them is left unable to determine what it is they're trying to do. The brake lights are on but he's accelerating? Once again - learn to drive, and drive predictably. It makes the roads a far safer and less stressful place for the rest of us.