Members of the Monaghan Roads Policing Unit conducted checkpoints on Saturday monitoring the large volumes of traffic heading for the Donegal Rally.
As a result of the checkpoints, a number of vehicles were stopped with illegal tints.
Effects of illegal tints reduce visibility, especially at night or in low light conditions and can hinder a driver's ability to see other road users and pedestrians, increasing the risk of collisions.
One vehicle in particular making its way to the rally was stopped for no NCT and seized.
Other offences for speeding and non display of N plates were also detected.
According to Gardai, fixed charge penalty notices will be issued to the drivers.