Comment Re:Even Better (Score 2) 433
In some cases, though, this is not pre-set.
Particularly here in the UK, a lot of traffic lights have (possibly capacitive) sensors buried in the road which detect the traffic passing over them. Lights will cycle early if no traffic is detected passing through a green, and/or if traffic is detected waiting at a red, especially at night when there is less traffic. That makes it hard to know in advance when they're going to change.
Another 2c from me: yellow times should depend on the speed limit.