I always drive at the speed limit, but I accelerate quickly to get there. Always amusing if there's someone behind me who obviously thinks I'm a slow and steady sort. When I pull away from traffic lights, they're often left behind, clearly not expecting me to accelerate so quickly. The only reason I bother keeping to the speed limit is paranoia that the police would be nearby. Generally quite calm on the roads although if someone does something that forces me to brake sharply when it was their stupidity that caused it and not anything else, it angers me. I remember one time when I was angry anyway, and there seemed to be a large amount of idiots on the road that evening, a pedestrian forced me to brake sharply when I had right of way, which caused me to scream some rather colourful words at them, which got an amusing reaction from my two passengers at the time (well, amusing looking back on it, not really amusing for an observer. They were just saying things like "Calm down!" and all that, seemingly unnerved by my little explosion).

But yes, provided I'm in a normal state of mind (i.e. not angry or depressed or whatever), I tend to be calm but assertive.