We’ve been looking into the impact that weather has on travel times using historical data from TrafficCast, specifically winter storms, like the one that hit the Atlanta area last month.

The day started off smoothly, with only a few commute-hour hiccups. By the middle of the day, many roads, particularly to the northwest of the city, had ground to a halt. The dots are reports of collisions or other traffic incidents, and a line that is twice as thick as the others means a road that takes twice as long to travel along as it normally does under good conditions.