Driving is one of the most potentially dangerous things people do on a day-to-day basis. You can’t remove the risk entirely; even if you’re the world’s greatest driver, you may still be involved in an accident that’s someone else’s fault. You can reduce risk by keeping your car well maintained, wearing your seatbelt and keeping to speed limits, but you also need to know how to respond to different conditions. One of the most challenging driving environments is low light – early morning, dusk and during heavy rain.
Most Driving Accidents Happen During Evening Hours
There are more accidents during the evening than at any other time of the day. This is partly due to increased commuter traffic, but if you compare the number of accidents per mile driven, the rate is still much lower during daylight. Late at night more serious or fatal accidents involve alcohol but this isn’t true earlier in the evening. So why do accidents happen as the light begins to fade? The answer is partly physiological, partly psychological.
What Happens To Our Vision When Driving At Night
When light enters your eye, it’s focused on the retina at the back of the eyeball. The retina is covered with cells known as rods and cones. Cones respond quickly to bright light and pass information about speed and distance along to your brain. Rods respond better than cones to poor light but are slower to pass messages to the brain, don’t pick up information about speed and distance, and can’t see color. As daylight fades, more of the work of seeing is done by rods. This means that before dawn or at twilight you cannot judge speed and distance accurately; it’s physically impossible for you to do.
How Our Minds Process Things Differently When We Drive At Night
Although your eyes take in information, you “see” with your brain. In other words, it’s your brain that makes sense of the messages from your eyes. If you’ve ever looked for your car keys only to find they’re right in front of you, you’ll know that sometimes your brain doesn’t do a great job of interpreting what your eyes are looking at. Crucially, you don’t realize your brain is doing this: it feels as though you’ve looked directly where your car keys are lying but not seen them.
When it’s getting dark your brain receives less information from the eyes and has to rely on memory and experience to interpret what’s happening. When you’re driving in daylight and you see a pedestrian in dark clothes standing under a tree at the side of the road, your brain gets enough information to say, “Slow down, there’s a person there who might step into the road.” In poor light, your brain gets a message that there’s a patch of darkness under a tree. You’ve learned that most trees have shadows but that most trees don’t have people under them, so your brain says, “OK, nothing there.” This isn’t a conscious process: what you experience is “seeing” an empty patch of shadow.
What can you do about this? The easiest thing is to drive a little more slowly. This makes it easier to react to other road users who apparently “come out of nowhere”. It also gives you a chance to look again. Remember that the rods in your eyes aren’t good at judging speed and distance. If you keep your eyes moving as you drive, scanning side to side, then your brain can get information about the same object from more than one point of view, making it much easier to judge position and speed. Slowing down gives you an opportunity to look twice.
Remember that everyone else on the road has the same kind of eyes and that they’re going to make the same mistakes. Turn on your headlights before you think you’ll need them, not to help you see but to help you be seen. Bright lights help other road users pick up information with the cones as well as the rods in their eyes, so they’ll be less likely to misjudge your, speed. But still be prepared for pedestrians and other drivers to make mistakes when the light is poor
Driving in poor light is more dangerous than driving in clear bright conditions because of the way your eyes respond to low light, and because of the way your brain interprets visual information. Drive more slowly, look more carefully, make yourself more visible and remember that everyone else has the same problem.