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Driver - Coping with Rain-Reduced Driving Vision

Rain poses a whole host of problems for drivers, but chief among them is reduced visibility.  Pooled water, flooding, hydroplaning, reduced braking power – these are all rain-induced challenges too, but without clear vision these hazards are even more dangerous.  So what’s the deal with rain, and what can you do to improve and/or cope with wet weather vision?

Rain scatters light

Raindrops scatter light as it passes through them, making everything appear darker than normal. That’s on top of the fact that when it rains, the sky actually is darker, so everything is that much harder to see.   The reduced light also diminishes a driver’s ability to see the contrast between different-colored objects, like the roadway and a silver car or a pedestrian wearing dark clothes.

Dim light also affects how the brain judges distance. Light from objects far away scatters as it passes through air molecules, making them appear hazy. When objects that are close-up are obscured because of the rain, they seem further away than they really are because your mind associates hazy images with long distances.

Then there’s the dreaded Mandelbaum Effect, a feature of the way the brain processes visual inputs.  When visibility is poor, scientists say, people naturally focus on objects within three feet of them.  That includes things like your dashboard and rear-view mirror, but, sadly, not what’s on the road.  The reduction in longer-range awareness also affects your peripheral vision, which is critical to detecting objects – vehicles, pedestrians – that may be coming at you from the side.

A silver lining in the clouds

When the roadway’s wet, you can see the reflection of brake lights two cars ahead of you from under the car you’re directly behind. Watching for this will give you a few extra seconds to react to people stopping up ahead. And, if you can’t see that reflection you’re too close to the car in front of you. 

Other than that, there’s not much in your favor if you’re stuck in a storm, but here are some ways to make your drive a little easier:

Keep it clean

Your windshield, that is. Fewer smudges mean less light scattering before it reaches you. Also, replace your windshield wipers if they’re getting old or leaving heavy streaks. The fewer things obscuring your windshield, the better.

Shed some light on the subject…

Dedicated daytime running lights only illuminate what’s right in front of the vehicle, so you need to use your headlights to see as far ahead as possible. What’s more, in an increasing number of places the law requires drivers to turn on their headlights any time the windshield wipers are in use.

… but don’t overdo it

High beams are counter-productive in rain.  Instead of helping you see farther ahead, rain will reflect more high beam light back into your eyes, making it harder to see anything. Don’t use your four-way, or hazard lights to let people know you’re driving slowly. Use them only if you’re stalled or stopped on the side of the road. Other drivers won’t see your brake lights as easily, and if they think there’s a disabled vehicle ahead they may swerve or stop short, potentially causing a wreck.

Take it slow

Despite how the guy behind you may feel about it, the best thing in the rain is to reduce your speed. Going a little slower lets you to pay more attention to your surroundings and give you more time to stop instead of having to brake hard, risking a skid or hydroplaning.  And in a downpour – when the rain is falling faster than your windshield wipers can clear it – your best bet is to pull off the road to a safe place and wait it out.