Q: Is it legal to have a strobe light on the front of your bicycle? In my experience, the strobe light is distracting and dangerous, and cyclists need to realize that while the driver is distracted by the flashing light, everything else disappears. Like a moth to a flame, drivers are drawn to flashing lights and nothing else.
A: Do you want to be noticed, or do you want to be understood? I know, it sounds like some faux-philosophical question posed by an aspiring Instagram influencer. Really though, it’s a question about lights.
If you want to be noticed, a blinking light works better than a steady light. At least, that’s what the research says. A study investigating the conspicuity of bicycle taillights at night found that drivers noticed cyclists with a flashing taillight three times sooner (at 123 meters) than cyclists with steady taillights (at 41 meters).
You’d think that settles it, but there’s a problem. It’s difficult for drivers to estimate the speed and distance of a cyclist using only a blinking light. The driver will spot you sooner, but they have a harder time understanding what you’re doing. A driver might misjudge the closing distance between them and the cyclist.
You mentioned moths and flames, and that’s sort of true, but not because of flashing lights. In the emergency responder world, there’s something called a secondary crash. From the name of it, you’ve probably already guessed that it’s a new crash that happens at the scene of an existing crash. Often, it’s a driver crashing into the emergency responder that’s on scene for the first crash. They’re pretty common too. Nearly ten percent of freeway crashes are secondary. This is a big deal for emergency responders, who are often the victims in secondary crashes. Researchers studied various lighting configurations on emergency vehicles (including no emergency lights). It turns out that flashing lights, steady lights, and even no emergency lights at all don’t make much difference in whether a driver is drawn to a crash.
The experts suggest that what we call the moth effect is really target fixation. That is, once a driver notices something unique, whether it’s lights or something else that gets your attention, there is a tendency to remain fixated on that object or situation, and where you look is often where you go.
Is it better to have a flashing headlight on your bike, or should you go with a steady light? In Washington the answer is pretty easy. The law prohibits flashing headlights on vehicles, and a bicycle is considered a vehicle in our state law. (Flashing taillights are allowed on bicycles.) If you want to be both noticed and understood, there is an option: modulated headlights. You may have seen these on some motorcycles. The intensity of the headlight pulses, but never goes completely off. Modulated headlights increase detection distance, and drivers can still perceive the speed and distance of the motorcycle. They’re available as bike lights, too.
So far, this has all been about getting seen by drivers. But headlights are also for seeing where you’re going in the dark. The best way to do that is to skip all the fancy stuff and use a steady light.
Bonus tip: If you really want to get noticed, (at least from behind) attach lights to the heels of your shoes and keep pedaling. We’re good at seeing biomotion (movement that indicates you’re looking at a human). Riders with lighted heels were seen from 220 meters away. The downside for people who like to coast: it’s only effective while you’re pedaling.