Three possible explanations for the low fatality rate:
- Bars, nightclubs and stores that sell alcohol must close by 2 AM, plus our other state and local alcohol sales regulations (particularly on hard liquor) are among the most restrictive of any state.
- The additional fatalities caused by the relatively high number of bad drivers are more than offset by forcing the silent majority of good drivers (and pedestrians) to maintain concentration and alertness.
- Many elderly drivers move to warmer states, and the ones who stay tend to be in better health than the ones who leave.
Edit: A fourth possible factor is that we're one of the most affluent states and cars succumb to corrosion faster than average due to the long, harsh winters (off the top of my head, I can't think of any state that's both more affluent and has longer winters), so cars are newer (therefore, safer) than average.