What are the rules for high beams on parallel roads or divided roads in the state of Washington? Does the 50-foot-wide median on the freeway negate the need to dim your high beams for an approaching car? What if the median is full of vegetation or has a wall that divides the freeway? What about a vehicle on a frontage road when there are cars on the freeway?
I’m going to make an assumption here; you’re asking this because you’d like to use your high beams as much as possible within the boundaries of the law. That makes sense. You can outdrive your low-beam headlights at surprisingly low speeds. Even high beams aren’t as effective at illuminating our path as we might hope. How ineffective? We’ll get to that in next week’s article. That’s right, this is a two-parter.
For now, let’s take a look at the law and see if we can find an answer to your question. Drivers are required to use headlights from a half hour after sunset to a half hour before sunrise, and any time conditions make it difficult to see people and vehicles 1,000 feet away. I’m continually bemused by laws where compliance involves humans making distance judgments. We’re notoriously bad at it. In one study that had people estimate roadway distances between 20 and 400 feet, no one was right.
But you don’t need to get out your giant tape measure. I have a better solution. My advice, while not required by law, is to always have your headlights on, no matter the time or the weather. You may not need them to see where you’re going, but it helps other road users see you coming. And that matters; using your lights during the day results in “a statistically significant reduction in fatal crashes.”
When headlights are required, they should be bright enough to “reveal persons and vehicles at a safe distance in advance of the vehicle,” with some limitations. One of those limitations is that when approaching an oncoming vehicle within 500 feet (another distance measurement we probably get wrong), drivers are to “use a distribution of light, or composite beam, so aimed that the glaring rays are not projected into the eyes of the oncoming driver,” or what the rest of us call low beams.
Side note: There are legitimate complaints about the amount of glare from low beams on many new cars. The law states that low beams “shall be deemed to avoid glare at all times,” which feels like the law is gaslighting us, saying, “There can’t be glare; I already said they’re fine.” Really, I think it’s intended to make it clear that by switching to low beams you’ve complied with the law. The problem is that our laws haven’t kept up with headlight technology.
Do you have to be on the same roadway as another car to be considered “oncoming?” Probably. The headlight law doesn’t make that clear, but elsewhere in the law “oncoming” only applies to vehicles on the same roadway. However, I think that misses the point. Regardless of how you interpret the law, the important question is, are my headlights causing glare for the other driver? Conceivably, some of the scenarios you described might not, but how can you know for sure? I suppose you’d know if they flash their high beams at you, but that’s an unreliable indicator. To be sure that your high beams aren’t impacting the approaching driver you can switch to your low beams. The trade-off, though, is less visibility for you.
