Roadside checks are being carried out on vehicles with tinted windows across the Teesside area.
Car windscreens must let in at least 70% of light
The Cleveland force on Monday launches its two-week long project, dubbed Operation Cameo, which it says is aimed at reducing accidents.
Spot checks using light meters will find out if cars meet regulations stating windscreens must let in 75% of light and side windows 70%.
Those found to be in breach of the regulations could face a £2,500 fine.
The operation will be mounted by the road policing unit of Cleveland Police and staff from the Vehicle Operators Service Agency (VOSA).
A Cleveland Police spokesman said: "Some vehicles have windows that are totally blacked out. The legislation is quite clear and says windscreens and the front passenger and driver's side windows must have at least 70% light transmission.
"We will be carrying out light meter checks on all vehicles we come across with blacked-out windows to ensure they comply with current legislation."
A VOSA spokeswoman said many drivers did not realise their vision was "significantly impaired" by tinted glass.
VOSA inspectors can issue prohibition orders forcing unfit cars to be towed away until the necessary adjustments have been made.