The RSA has no difficulty with modifications so long as they don’t impair the safety of a vehicle, comply with the law and are not a nuisance to the public. To reflect the fact that some modifications can have wider negative impacts, we've added two additional tests to the NCT.
Excessively tinted windscreens or front side windows present a significant safety hazard for vehicle drivers and their occupants. Visibility is greatly reduced, particularly for night time driving and at times of low light. There are also enforcement issues for An Garda Síochána in regard to driver recognition, the detection of driving offences e.g. holding a mobile phone while driving, and other criminal activity.
If the NCT vehicle inspector deems that the windscreen or front side windows are excessively tinted the level of light transmission of the window will be tested. The glass in the windscreen and front side windows will be required to have a light transmission level of not less than 65% in order to pass the NCT test. Unfortunately the National Car Testing Regulations do not allow for any exemptions in this regard.