The freeway system uses ramp meters to help keep traffic moving.

Operators will manually tune the ramp meters if necessary.

In recent years, many states have used technology like cameras, message boards and ramp meters to direct the flow of traffic.

In 2000, the ramp meters were turned off for a study period mandated by the Minnesota Legislature.

There are about 430 ramp meters and more than 450 traffic cameras in the Twin Cities metro area.

Several ramp meters began operation in 2008 in metro Atlanta.

In normal operation of the ramp meters, only the red and green lamps are used.

The study involved shutting off all 433 ramp meters in the Minneapolis-St.

There are plans to install ramp meters on every on-ramp in the Japan motorway system.

Freeways in Taiwan use ramp meters during peak hours since 1993.