Flashing vs Steady Bike Lights

Are flashing lights better than steady ones?

Bike lights are available in two main categories.  They are designed to make bike riders be seen by other people who share the road, or they are manufactured to help riders see better.

Typically, the operating modes for bike lights include low, medium, and high beams, and optionally,  a flashing strobe option. Whether one light is better than the other depends on the circumstances. For instance, a flashing strobe provides greater visibility on straight roadways. Steady or constant stream bike lights are better when riding in the dark when the path before the bike needs to be illuminated to prevent hitting things along the way.

Bike regulations

The regulations regarding flashing vs steady bike lights vary from place to place. For instance, in the UK, riders may only use strobe lights that flash at between one and four flashes every second. In Germany, strobe lights on bikes are prohibited. This goes for both the front and back of the bike, stating that the flashes can distract other users of the road. Strobes are also prohibited in Austria and in the Netherlands.   In some locations, strobes are allowed, but for emergency vehicles only, because they alert other travelers on the roadway that an emergency situation is underway.

In the US, laws are determined by the individual states. For instance, Washington state bike regulations allow the use of flashing white lights, but only by emergency vehicles. However, in some states flashing lights are allowed, and in others they are actually required.

Which lights are better, flashing or steady?

study conducted by Clemsen University suggested that the flashing light was far more visible on straight roads after dark. In fact, drivers could see riders with flashing lights at three times the distance than that provided by the steady light.   Since the human eye is better at seeing things that move or at changing stimuli, eerier detection when a rider is using a strobe makes perfect sense.

In his interview with Bike RadarMarc Green, an expert on determining the roles that humans play in collision analysis pointed out that it can be harder to determine a bike’s distance when it has a flashing light.  It is also hard to tell how fast the bike is traveling.  People experience difficulties determining depth perception when a bike is adorned with a strobe after dark.  The brain does not respond to them in the same way because it requires fixed objects around them to make determinations about depth perception.  It has been suggested that attaching a steady light to the backs of one’s cycling shoes can help remedy this depth perception problem.

A flashing bike light does not light the path or roadway in front of the rider well enough to prevent accidents to any degree of certainty.  This is especially true of mountain bike riders who ride rocky paths after dark.  They need a bright, steady lamp that provides a lot of room  in front of them so they can avoid tree roots, holes, animals and rocks along the way.

While flashing lights might be better attention grabbers, a constant stream of bike lights deliver constant information about the biker’s location.  It is easier for a driver to see a blinking light in the dark, but it is easier for that same driver to make a determination in feet about how far away the bike is located if a constant stream of light is used.

Daytime Biking

Although daytime bike lights are not legally required, the accident rate for bikers with lights  is around 19% lower than those without lights. During the time of day when the sun is brightest, it can be more difficult to get a driver’s attention than after dark. In this case, a flashing pattern might do the better job, especially if the light has a higher lumen intensity.  The light mount for a flashing light can be adjusted into positions that are more apt to be visible to drivers.  While steady lights can also be seen with a high lumen count, the thing that makes the biggest difference is the illusion of motion that the flashing produces.  This registers in the brain at a faster rate during the daytime hours than one constant beam of light.

Flashing vs steady bike lights and safety issues

In recent years, much has been written about the safety, or lack thereof, of the strongly lit flashing vs steady bike lights and the safety ramifications of each.  Today’s bike lights have very high lumens and can compete with any car headlights.  This can man something critical to oncoming traffic.  Flashing bike lights with a high lumen count can distract a driver or cause discomfort to cars driven in oncoming traffic.  Steady lights with high lumen counts are not as distracting, as they do not give the same illusion of movement that high lumen flashing lights do.

Flashing bike lights can also have a negative impact on drivers with epilepsy when they have a variety that is sensitive to light.  It is rare for epileptics to experience photosensitivity, but some do, and it cannot be determined ahead of time whether a car will have a person with photosensitive epilepsy at the wheel.  A steady light is much less likely to trigger a negative safety issue in this instance than a flashing light.

Additionally, flashing lights can create a very uncomfortable and dangerous riding experience for oncoming bikers who might feel blinded by the overwhelming intensity of the beam.  Sometimes, riders will come to a halt at a stop sign while facing an oncoming bike with a bright flasher and will be temporarily blinded by it, as would anyone whose eyes have encountered a strong light.  Those few seconds after exposure are long enough to cause an accident once the oncoming biker has remounted and tries to ride.

The Bottom Line

When it comes ot flashing vs steady bike lights, the rigor should gauge the situation and act accordingly.