With snow expected to start falling and the District sure to empty out ahead of the afternoon rush, the D.C. Department of Transportation wants you to know which roads are safe to drive on.

To that end, this afternoon DDOT turned on its Roadway Weather Information System, a network of monitors that measure air temperature, wind speed, visibility and surface temperature on various roads.

For example, a RWIS monitor on the Chain Bridge reports that the air temperature is a shade over 42 degrees, visibility is 1.1 miles and the temperature of the road surface is 49.1 degrees. You can also get pictures of the road that are regularly update; the picture of the Chain Bridge above was taken at 1:20 p.m.

DDOT has also announced that it has set street lights to rush hour timing and deployed additional traffic control officers to speed the exodus out of the city. It is also recommending that if you have to go, you’d best be on your way before 3 p.m.