KANSAS CITY, Mo. -- If this month's almost constant stream of winter weather has been tough to drive through, it's been just as hard for transportation officials in urban areas trying to keep the icy roads safe.

The waves of heavy snow and ice, combined with power outages that shut down operations in Kansas salt mines, have sapped supplies of salt used by road crews to keep highways and streets passable.

The Kansas Department of Transportation said it is down to 800 tons of salt to treat 2,000 miles of highways in Johnson, Wyandotte and Leavenworth counties.

On Friday, as the Kansas City area's fourth major storm in December dumped up to three inches of snow, the department used sand to supplement its salt supply.

That led to some roads being slicker than usual and contributed to a rash of accidents. The Kansas Highway Patrol reported 30 crashes between 6 a.m. and noon in the Kansas City area. On the other side of the state line, the Missouri State Highway Patrol said it had worked 31 accidents by 2 p.m.

"The result of [using sand] is the roads are taking longer to melt off," said KDOT spokeswoman Kim Qualls.

The Missouri Department of Transportation has used 70 percent of the 48,000 tons off salt it had set aside for the eight-county metro Kansas City area.

MoDOT road crews are using straight salt on the interstates.