How Well Can You See Ahead?
Many users are confused about when to use of low beam and high beam headlights.
Think about this: low beams let you see about 200 feet ahead. It can take about 200 feet to stop when you drive at 30 mph. That is almost half a city block in length. If you cannot see 200 feet ahead, you may not be driving safely at 30 mph. By the time you see an object in your path, it may be too late to stop without hitting it.
Headlights on “upper” or “high” beam let you see about 350-400 feet ahead. 400 feet is your approximately stopping distance when driving at 50-55 mph. That is about the length of a city block.
In other words, high beams let you see twice as far as low beams.
When to Use High Beam Headlights
In any situation when you cannot see well enough ahead, you should start by slowing down. Remember the basic speed law and the two-second rule. When you cannot see well enough, you must increase your following distance which means more seconds. If there are no oncoming vehicles, turn on your high beam headlights.
In general, you should always use high beams outside cities and in rural areas, as long as there are no other vehicles around. Dim your lights when there are oncoming vehicles, or when you are approaching another vehicle from behind.
During poor visibility it is particularly important to use high beams on unfamiliar roads, on dark city streets, in construction areas, or where there may be people or bicyclists along the side of the road. Remember to adjust you speed and not overdrive your headlights.
You must also dim your headlights in all situations when there is a risk of blinding other drivers with your high beams.
Exception from the Rule
Sometimes, however, high beams will not improve your visibility. In fact, it will do the opposite.
This happens in fog, heavy rain, and snow. In these situations, the light from your high beams will reflect back from the fog/rain/snow and cause glare. The glare will make it more difficult to see ahead. To improve visibility, switch to low beams.
Some vehicles have fog lamps that may be used in combination with low beams. Fog lamps will illuminate road edges and pavement markings, making it easier to stay in lane. The should only be used in heavy fog, rain, or snow. Turned them off during normal driving conditions.