A little trick that has served me well is to sit down when you have some time and visualize, as vividly as possible, some hazardous scenario. Maybe someone left turning (right in UK) in front of you or someone running a stopsign/redlight etc. Play it through several times, working in different ways of dealing with it, trying to find the best for this particular situation. Then change things a little, maybe speed up or slow down the idiot who is about to run you down, add or delete other traffic, etc. and do it again. This is rather like practicing a particularly difficult pool shot because you may need to be able to handle it. If one of the situations you have worked over like this ever does come up, you will already know how best to deal with it and will have pre-programmed your reflexes.
