Vaelroth: And I agree that "obligatory" is harsh. The decision is harsh. But you are morally compelled to do it because it is right, even if you fell crummy doing it. That's where the compassion comes in: you feel for the person you kill (and likely you'll feel guilty until the day you die) but it was still the right thing to do.
Chuck: And that's why ethics intrigue me so.
Anyway, I'm not advocating a straight count of lives. That's just one factor in determining who dies. I just give the right to life a lot of weight in how I decide. There are a lot of grey areas. In the scenario you give, for example, I would say that the driver is right to avoid hitting the drunks but that the drunks are wrong for running out into the street. The driver is not morally responsible for your death because he was doing his moral duty. The drunks are responsible for your death because they caused the driver to swerve while not doing their moral duty. That's where I'd slot responsibility in.