Don't forget about a population density. I suspect a lot of the 'ratial' bias in the justice system stems from the number of interactions with poor people in high vs low population areas. In some areas you could sit on your back porch target practicing with a shotgun and nobody would care. That's not the case in any city.

Get drunk and drive off the road into a corn field, well if you can get out without anyone noticing then no big deal.