If you get tripped on the speed trap approaching a red signal, you are going too fast to be able to comfortably stop at the red. You want to aim to be doing between 20 and 30mph when you pass the speed trap, and between 10 and 15mph when passing the AWS. There is no point rushing up to a red signal and barely stopping in time, you'll just end up waiting longer for it to clear, and if you apporach slow, the chances are it will clear before you reach it, then you will get a rolling start, rarther than having to start from a stand (very useful with heavy trains, especially when rail conditions are poor). With freights though, you need to be even slower, and the speed trap trip speed for locos is lower (2/3 of the passenger speed I think) when pulling frieght than passenger or light engine. So far only the 66 simulates this, but hopefully other locos should have this feature aswell eventually.