What are your opinions on driving manners?

As a soon to be MD, I'm very careful about driving after all the trauma cases I have seen (i.e. signaling in good time, checking all my spots, driving in reasonable speed). But here and there, you see a reckless driver that just irks me! A couple times I have tried to switch to a lane, made sure there was good space after checking the blind spot after signaling, and as I transferred, there is a car speeding by and nearly missing you! Once the car had to use an emergency lane, another time I had to slam on my brakes and a semi was behind me (which takes a longer time to slow due to momentum). There was nearly a three car accident! How can anyone rationalize the possibility of a life threatening car accident just to save 2 seconds? Most annoying thing and from a physician's standpoint, it does make it harder to sympathize with some trauma patients, albeit there are often people who are generally pretty innocent and unfortunate. Discussion?