Car Window Tinting: Five Mistakes New Zealand Drivers Make

11 January 2016
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Car window tinting is increasingly popular with New Zealand drivers. Tinted windows can help cut glare while driving, and your air conditioning won't need to work so hard to keep you and your passengers cool. Nonetheless, certain laws in New Zealand restrict the use of tinting, and it's important to make sure you don't fall foul of the rules. If you're thinking of tinting your car windows, avoid the five following mistakes that other drivers sometimes make.

Applying a tint that is too dark

A lot of drivers think that tinted windows look cool, but it's also important to remember that this modification can make it more difficult to drive safely. If the tint is too dark, you may find it more difficult to see other road users, especially when driving at night. For example, poor visibility could mean you fail to see a vital road sign, a cyclist or a pedestrian until it is too late.

In New Zealand, the darkest legal tint you can have is 35 percent visible light transmittance (or VLT). This measurement tells you how much light the material allows to pass through the glass. 

Tinting the entire windscreen

You cannot legally apply tinting film to the entire windscreen. In fact, the only tinting overlay you can legally apply is an anti-glare band.

Even then, you can only apply an anti-glare band to a certain part of the windscreen. These additions cannot extend lower than your sun visors when folded flat, and you cannot have an anti-glare band more than 100mm lower than the top of the windscreen. 

Assuming the rules only apply to the front window of a car

Of course, visibility through the windscreen is the driver's top priority, but you also need a good view from every other window in the car. Unfortunately, some drivers wrongly assume that the VLT restriction only applies to the front windscreen. In fact, in New Zealand, the 35 percent VLT rule applies to every window in a passenger car.

The rules change for some types of vehicle. For example, if you drive a van or an SUV, you can apply a darker tint to any window behind the driver's door. For these vehicles, visibility from these rear windows isn't so important.

Miscalculating the VLT when applying a window film

If you buy a window film that offers a VLT of 35 percent, you may still end up driving illegally by using this film on your car. Manufacturers normally modify the glass they use in cars to block out a certain amount of light. As such, if you then block out more of the light with a window film, you will probably end up with a VLT that falls below the legal limit.

For example, assume the manufacturer installs glass with a VLT of 85 percent, and you apply a film with a VLT of 35 percent. The VLT of the tinted glass is now just under 30 percent. 

1 – The original glass started with 100 percent VLT.

2 – The manufacturer restricted this to 85 percent.

3 – You then applied a film that allowed 35 percent of the light to pass through glass that only allowed 85 percent of the light to pass through.

4 – You would calculate the true VLT as 0.35 x (100 x 0.85) = 29.75 percent VLT.

In this way, you can see how some drivers mistakenly apply a tint that is too dark. 

Assuming the police won't catch you

Given the safety risks that excessive window tinting can cause, the New Zealand police routinely check glass tinting that they believe is illegal. A police officer can use a calibrated VLT meter to check the light transmission through your windows. If the reading is too low, you could end up in trouble.

A professional window tinting company will also have one of these meters. Following installation, the fitting company can also apply an official VLT label to the glass. You don't have to have one of these labels, but if an officer can see one, he or she is less likely to inspect the car further.

Window tinting is popular with New Zealand drivers, but the rules about these modifications are strict. Talk to a professional car window tinting business for more information and advice.