Fog
Yesterday was the first time in a long time that I’ve needed to turn my lights on when driving. Normally my car takes care of that for me. Ah, technology, isn’t it wonderful? It now saves us the hassle of reaching for the lights/indicator lever by the steering wheel - as if it were somehow a burden…
Anyhoo, as I drove my wee munchkin to ‘little school’ yesterday, and then myself to ‘big school’, my car decided it was bright enough that lights weren’t needed. I overrode the all-knowing logic of my car and turned them on anyway. I could see just fine - but it was foggy. I could barely see more than 100 m in front of me as I drove along. Turning my lights on made for a safer drive. Not for my ability to see the road, but for oncoming cars to see me.
Here’s a thought - car lights are not just so you can see the road. They make it that much easier for you to be seen by others. The same can be said for bicycle lights. When you ride a bike at night, lights play a large role in you being seen, and are not just for the benefit of your vision.
So, this whole “lights on when you drive through fog” business. Yes, it is a good idea, so you are more visible to drivers of other cars. But have them on low beam, not high beam.
But wait, wouldn’t high beam make me even more visible to other drivers?
What you have to consider is that you also want to see the road.
Fog is a colloid. A colloid is a type of homogeneous mixture, meaning its composition in constant throughout. Suspensions and solutions are other types of homogeneous mixture. The three types differ in particle size. For suspensions, the particle size is greater than 1000 nm (nm = nanometre = a billionth of a metre). For solutions, the particle size is at the molecular or ionic level, 0.1-2 nm. Colloids lie in the middle, with particle sizes from 2-1000 nm in size. Colloids often appear opaque or murky because the particles are large enough to scatter light.
And this is why you should have your lights on low beam when driving through fog. If your lights are on high beam you are basically shining them into the fog right in front of you. The fog can act as the good colloid that it is and scatter the light, and you end up looking at a white wall of fog.
All you need do is have your lights on low beam, and they will be directed downwards at the road in front of you. You can still see where you are going, and it is enough to be easily seen by other drivers.
So when driving through fog, lights on low beam.