Motorists on Missouri's Interstate 270 yesterday experienced for the first time an enforced speed limit that was lowered by remote control. Under a new variable speed limit program, the Missouri Department of Transportation (MoDOT) installed electronic signs that allow officials to reduce the maximum speed limit on particular sections of road by as much as 20 MPH from the basic 60 MPH speed limit. Motorists who may have missed the sign, perhaps obscured by a passing semi truck, risk being ticketed if they continue driving at 60 MPH.

"A defensive driver, who is paying attention to the road, should be able to pay attention to the speed limit signs, important messages on the overhead message board, his or her speed, as well as paying attention to the other drivers on the road," the MoDOT website explains. "The Missouri Highway Patrol has the primary responsibility of enforcing those speed limits. They have indicated that they will support the reduced limits and will be using various methods to track speeders and issue tickets."

The transportation department spent $900,000 in gas tax funds to purchase the complex equipment required to administer the system, insisting its sole motive was to help reduce congestion, not increase traffic citations. A computer program monitors average road speeds from and makes "suggestions" on when to reduce the limit and when to allow it to return. A live MoDOT employee at a Transportation Management Center can accept the reductions in 5 MPH increments down to 40 MPH -- the minimum speed limit allowed under state law. The system must also wait five minutes in between each change. Officials insist the speed difference between any two of the seventy speed limit signs will never be more than 15 MPH.

Delaware, Michigan, New Jersey, Tennessee, Washington and Wyoming have also experimented with forms of variable speed limits.