RIDGELAND, S.C. – As Interstate 95 sweeps past this town along South Carolina’s coastal plain, motorists encounter cameras that catch speeding cars, the only such devices on the open interstate for almost 2,000 miles from Canada to Miami.

The cameras have caught thousands of motorists, won accolades from highway safety advocates, attracted heated opposition from state lawmakers and sparked a federal court challenge.

Ridgeland Mayor Gary Hodges says the cameras in his town about 20 miles north of the Georgia line do what they are designed to do: slow people down, reduce accidents and, most importantly, save lives.

But lawmakers who want to unplug them argue the system is just a money-maker and amounts to unconstitutional selective law enforcement.

“We’re absolutely shutting it down,” said state Sen. Larry Grooms, chairman of the Senate Transportation Committee.

Recently, Ridgeland Police Officer David Swinehamer sat in a van beneath an overpass as a radar gun in a thicket of electronic equipment outside clocked passing vehicles: 60, 72, 73, 67.

Then a Mercedes with South Carolina plates sped by going 83 — 13 mph over the speed limit. A camera fired and pictures of the plate and driver appeared on a monitor in the van. The unaware motorist continued north but could expect a $133 ticket in the mail in a couple of weeks.

Motorists do get a warning. As they enter town, a blue and white sign says they are entering an area with “Photo-Radar Assisted Speed Enforcement.”

Speed cameras are used in 14 states and the District of Columbia, according to the Insurance Institute for Highway Safety. The only other place with a camera on I-95 is in a Maryland work zone.

Last year, Arizona ended a two-year program with cameras on Phoenix-area expressways and other roads, in part because of perceptions they were being used to raise revenue.

But Cedar Rapids, Iowa, began using cameras last summer on busy I-380. Police there said during the first month of operation, violations dropped 62 percent.

Hodges said in Ridgeland from January to July of 2010, there were 55 crashes and four fatalities. From August through the end of last month, there were 38 crashes and no deaths. And since the cameras started operating until last month, there has been almost a 50 percent drop in the number of motorists driving 81 or more.