MINNEAPOLIS (AP) -- Minnesota transportation officials are testing new technology to catch carpool lane cheaters.

Through September, the State Patrol issued nearly 3,500 citations to drivers who illegally used the lanes reserved for two or more people, buses, motorcycles and solo drivers who pay to use them. That compares with 2,933 citations in all of last year.

The Department of Transportation is testing a system of beacons and detectors during the morning rush hours on Intestates 35W and 35E. As a driver with a valid carpool tag passes an antenna, it flashes blue. An amber light flashes if the antenna does not detect a tag. A trooper must determine a vehicle has only one occupant before making a stop.

A citation can cost carpool lane cheaters up to $300.