Mine goes up because of idiots that don't slow down in snow/ice, people who "left" you, people that wait at a green light w/o entering the intersection, and red light runners. Getting "lefted" is way less common than it was a few years ago, it's when the car facing you in an intersection and is first in line guns it across the intersection on green, cutting you off. Common at certain intersections. And the green light waiters make it inevitable that you sit for multiple light cycles at an intersection.