In Minneapolis, carpool lanes are free during morning and afternoon rush periods for buses, motorcycles and vehicles with two or more occupants, while drivers who are alone in the car must pay a toll to use them.

State officials estimate that about one in six motorists using the toll lanes in 2019 were single occupancy vehicles not paying the toll. To help state troopers identify carpool lane cheaters, MnDOT is spending $370,000 to install 24 sets of flashing beacons and tag readers at 19 sites along across the metro area, including ten on I-35W south of downtown Minneapolis, eight on I-394 and six on I-35E. 

As a vehicle passes a checkpoint, an antenna seeks to read a MnPass tag. If a driver has a valid tag, a blue light flashes; if no tag is detected, an amber light flashes and a trooper must visually determine whether the vehicle has only one occupant. The trooper can then check to see if the driver has a valid tag and whether it was set to allow MnDOT to collect tolls. If the driver does not have a tag or has it turned off, they may get a ticket and owe a fine of up to $300.