If it's snowing on a Tuesday, you might think about taking the bus.

Over the past four years, according to state traffic crash data, Tuesday is the most accident-prone day of the week when it's snowing or sleeting in Champaign and Vermilion counties.

In both counties, from 2007-2010, snowy Sundays were the safest days to drive.

As the area braces for the onset of winter, state police and transportation officials issued their annual call for drivers to take extra precautions.

The reason is simple: Cars don't move as well on slick roads as they do on dry pavement.

Among their suggestions:

— Slow down. Lower visibility and slick roads make for a dangerous combination. "Driving too fast for conditions is the leading cause of traffic crashes during the winter season," said the state in a news release.

Numbers back that up: The lion's share of the accidents in winter are when a car skids into an object, hits another car from behind, or sideswipes a car going the same direction.

— Watch out for exit ramps, curves and bridges. All of them can develop "black ice" — a thin coating of ice that can be hard to see. In addition, because cold air circulates above and below bridges, ice forms on them earlier than on other kinds of pavement.

— Don't slam on the brakes or make quick direction changes, including sudden lane changes. Either action on ice increases the chances of losing control of a vehicle.

— Don't follow too closely. The more room between you and the vehicle ahead of you, the better chance you have of stopping if you need to.

— Wear your seat belt. The National Safety Council says seat belts saved 75,000 lives between 2004 and 2008. There's good news here: Seat belt use has risen from an average of 69 percent in 1998 to 88 percent now.

— Check the roads before you go, online at http://wrc.gettingaroundillinois.com or by phone at (800) 452-4368 (for interstate routes).

The Transportation Department says it has a full supply of road salt. Officials urge drivers to be cautious when driving near snow plows.

Some winter driving facts, based on accident data compiled by the state Transportation Department:

1,405: The number of accidents in snow or sleet in Champaign County from 2007 through 2010.

605: The number in Vermilion County.

219: The number of injuries in those accidents in Champaign County.

119: The number of injuries in Vermilion County.

5: The number of fatalities in Champaign County.

3: The number of fatalities in Vermilion County.

East: The most common direction of travel for one-vehicle accidents in Champaign County.

West: The most common direction of travel for one-vehicle accidents in Vermilion County.

735: Accidents during daylight in Champaign County, with another 218 during darkness but on lighted roads.

341: Accidents during daylight in Vermilion County. Another 98 happened during darkness but on a lighted road.

485: Collisions with "fixed objects," the single biggest type of collision in Champaign County. Followed by 285 rear-end collisions, and 135 sideswipe wrecks where both vehicles are going in the same direction.

290: "Fixed-object" collisions in Vermilion County, followed by 77 rear-end collisions and 49 collisions at an angle.

982: Number of accidents away from intersections in Champaign County. (423 at intersections.)

430: Number of accidents away from intersections in Vermilion County. (175 at intersections.)

I-57: The highway with the most accidents in Champaign County, at 251. I-74 right behind at 234, U.S. 45 is at 103 and U.S. 150 is at 77. No real surprise there: They are the busiest roads in the county.

I-74: Leading highway for accidents in Vermilion County, with 170. U.S. 136 is second with 84. U.S. 150 is at 65, and Illinois 1 is at 16. As with Champaign County, these are the busiest roads.

This story appeared in print on Dec. 4.