How to stop glare while driving

Four sources, four fixes

The one nobody diagnoses

Look at your windshield on a bright day and you may see your dashboard reflected in it — a ghostly image of the dash top, sitting in your view of the road.

It happens because a windshield is steeply raked, so it acts partly as a mirror for whatever is beneath it. A dark matte dashboard reflects very little. A dashboard that has been treated with a glossy protectant, or one with a shiny vinyl finish, reflects a great deal.

This is the strongest practical argument against the shiny interior dressings the detailing aisle is full of. A glossy dash looks freshly cleaned in the driveway and puts a reflection in your eyeline every sunny day afterwards.

The fix is a matte protectant. 303 Automotive Protectant publishes an SPF 40 equivalent rating and dries to a matte finish specifically, which is the combination you want: UV protection without the reflection. Meguiar's Ultimate Interior Detailer also finishes satin rather than glossy. The comparison is in best dashboard protectants.

Night glare is almost always your windshield

Oncoming headlights that produce a starburst, a halo, or a smear across the glass are generally not the other driver's fault. They are a windshield problem, and there are three contributors.

• The interior film. Interior plastics off-gas in a hot cabin and condense on the coolest surface, which is the inside of the windshield. That film scatters light, and scattering is what turns a point of light into a starburst. It builds so gradually that nobody notices
• Pitting. Years of road debris leaves thousands of microscopic craters in the outer surface. Each one scatters light. Pitting is not cleanable — it is the reason an old windshield is worse at night than a new one, and the only fix is replacement
• Wiper smear. Worn blades leave a film that is invisible in daylight and catches every oncoming headlight at night

Cleaning the inside of the glass properly is the cheapest and most effective intervention here, and the result surprises people — the first cloth comes away visibly dirty from glass that looked clean. The method is in how to clean car windows without streaks.

If cleaning does not fix it, hold a light at an angle across the outer surface and look for pitting. If the glass is heavily pitted, no product solves that.

Polarized lenses, and where they backfire

Glare off a wet road, a car roof or a body panel is largely polarized light, and polarized sunglasses block it specifically. For low-sun driving they do something no tinted lens can.

Two limitations worth knowing. Windshields are laminated, and the interlayer can interact with polarized lenses to produce visible patterns or blotches in the glass — mildly distracting rather than dangerous, but real.

More significantly, polarized lenses can make some LCD screens hard or impossible to read at certain angles, and modern cars are full of LCD screens. If your instrument cluster or head unit goes dark when you tilt your head, that is why.

Sun on a passenger

A different problem with a different product. A rear passenger in afternoon sun cannot move out of it, cannot reach a visor, and — if it is a child — cannot do anything but be unhappy about it.

A stretch mesh side shade covers the whole door aperture and still lets the window open, which is the failure of every suction-cup panel. It is a screen rather than a blackout, and EcoNour does not publish a UV-blocking percentage, which we would rather state than fill in. See best side window sun shades.

Note that this is the passenger's problem rather than the driver's. Anything on the front side windows is subject to visibility rules in many states, and it is also in your own field of view for mirror checks — the same reasoning as in where to mount your phone in a car.

The parked car version

Glare when you first get in is a different thing again: a dashboard that has been in the sun for hours is both blindingly bright and roughly 60-70 C, and a hot glossy dash is the worst possible reflector.

A windshield shade solves the temperature and the immediate glare together, and it also slows the UV degradation that eventually cracks a dashboard — which is the same reason to use a protectant. Both are covered in best windshield sun shades and how to protect your car interior from sun.

What to do, in order

• Clean the inside of the windshield. Free, and it is the fix more often than anything else
• Look for a dashboard reflection and switch to a matte protectant if you find one
• Replace worn wiper blades. Cheap, and smear is invisible until dark
• Clear the dash top of anything glossy or light-colored
• Buy polarized sunglasses for low sun, accepting the LCD trade-off
• Add a side shade if the complaint is a passenger rather than you