Seizure-Inducing Bicycle Lights

Flashing Bicycle Light


Granted, the photo at the top of this post isn’t the finest representation of those blindingly blinking headlights which have become so common on bicycles today. But without hauling out semi-professional photographic gear, this was as close to capturing the pulsing light as I could come.

With each passing day, it seems, these lights become brighter. New technologies allow greater output in increasingly smaller casings. And, the flash patterns vary. Some lights offer more than one pattern. Others offer only a single pattern, but it’s an off-beat sort of pattern, that is not only attention-getting, but highly annoying.

But, perhaps that’s the point. An annoying light is difficult to miss. And, if the light isn’t missed, neither is the bicycle. Or so the theory goes.

There are pros and cons to such lights. Under certain conditions, where a bicycle might be difficult to see, they draw a driver’s attention to the spot where the cyclist is riding. Examples of times where this might be beneficial are in heavy traffic, when a driver’s attention is divided in multiple directions and on dark roads where a driver might not expect to see a bicycle.

At times like these, flashing white lights might mean the difference between a car noticing a bicycle and avoiding it and a car not noticing anything in its path and striking a bicycle. So, there is a definite safety advantage in situations where a bicycle might not be otherwise seen.

But, what about cases when people ride on moderately trafficked suburban roads with decent lighting, less congestion and greater opportunity for drivers to notice their surroundings? Are flashing lights necessary in such settings?

This is debatable. Under these conditions, wearing brightly colored clothing might be enough to get a cyclist noticed. Even in the dark, light clothing stands out in a car’s headlights. And, reflective accents or vests can catch a driver’s eye.

In essence, multiple methods exist for making a bicycle visible. Yet, the flashing white lights have continued to grow in popularity, more than any other visibility creating method.

Despite the success of these lights in gaining the attention of everyone facing the bicycle where they are mounted, a downside exists. Strobe lights can cause some people to have seizures.

Contrary to popular belief, not everyone who suffers from seizures is sensitive to flashing lights. And some individuals who are not prone to having seizures can become dizzy or possibly have a seizure, if they are unusually sensitive to bright, flashing lights.

This concern has been cited as a reason for reducing the use of flashing bicycle lights. While these concerns are well-intentioned, the fears of their proponents may be overblown.

There is a big difference between seeing a small flashing light at a distance and having a large flashing light or several flashing lights directly in front of one’s eyes. Individuals with seizure disorders know what triggers their seizures. And, they try to avoid those things.

It really isn’t very difficult to look away from a small flashing light on the front of a bicycle. And, the percentage of people with seizure disorders who are sensitive to flashing lights isn’t extremely high. Therefore, the odds of a person with this disorder coming into contact with a bicycle using a flashing light is fairly small. And, yet, these lights are frequently referred to as “seizure-inducing.”

What it boils down to is that these lights have been colloquially connected with a medical condition because some people are irritated by them. Rather than referring to the lights as annoying, when they would prefer that no one used them, they imply that these lights are doing a disservice to those with a particular medical problem.

It’s a way of making something they dislike look unacceptable without coming right out and saying so. Nonetheless, cyclists should try to regard the use of these lights as a positive thing, even if, on an individual level, they don’t like them.

As irritating as these lights may be, they make the cyclists using them feel safer. Feeling safer means that they are more likely to ride their bikes on the roads. This increases the total number of bicycles on the roads, which benefits everyone — even though some drivers refuse to admit that this benefits them too.

With so many would-be cyclists citing fear of riding in traffic as a primary reason for not using a bike for transportation, we should be more forgiving of safety promoting behaviors which make cycling seem less dangerous. After all, how many times have we heard a driver use as an excuse for hitting a bicycle: “I never saw the bicycle.”

How likely is it that this excuse will be believed when the bicycle in question was sporting a blinding, “seizure-inducing” light? Not likely. More likely than not, the driver wasn’t paying attention or was driving recklessly.

On more than one level, flashing lights provide safety — by giving a cyclist a psychological edge and by creating a situation where a driver can’t claim to not have seen the bicycle he hit. Momentary irritation on the part of oncoming traffic is a small price to pay for a cyclist’s peace of mind and for potentially saving her life.

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4 Responses to Seizure-Inducing Bicycle Lights

  1. Lee Hollenbeck says:

    Couple of comments here. When I am driving my car, the bikes I notice the most have blinking lights. I like to have 2 handlebar lights, steady and blinking. Also my new cygolite metro light has a nice feature, a steady light with a momentary flicker. Works great.

  2. James Haroldson says:

    There is scientific evidence that suggests a flashing light is harder for the human eye to judge in terms of location and distance than a fixed beam equivalent.

    ‘A target moving physically in discrete spatial jumps could elicit smooth tracking eye movements in practised observers, but this tracking was increasingly interrupted by saccades when the temporal interval between the spatial jumps of the target was greater than 150 msec.’

    “Smooth eye tracking and the perception of motion in the absence of real movement” by Morgan and Turnball, 1978

    Also some of these lights are now the equivalent of a camera flash bulb going off repeatedly. Ask any film star how disorientating that can be.

    White flashing lights do disorientate which should not be the aim of a cyclist.

    Oh by the way I am an epileptic so I’d like to correct a few assumptions made here.

    Firstly Epilepsy is a disability (very important thing to note).

    Not all epileptics are sensitive to strobes but these who are have varying degrees of sensitivity.

    For myself I am not usually at risk of a seizure from flashing lights but it does cause severe discomfort and can increase the affects of disorientation plus induce headaches.

    Normally the feeling when I encounter a bright flashing light is the equivalent to being punched in the face every time the light flashes. It’s not pleasant but it’s also not necessary for a cyclist to inflict this on me when they can use a fixed beam light instead.

    The author suggests its not difficult to look away from the flashing light. Well what if that light is on a bicycle riding towards me?

    Are people meant to close their eyes or not look in the direction that they are travelling whilst the offending light is in view (which can be for up to 30 seconds)?

    Wouldn’t averting ones eyes whilst driving a car or riding a bike be dangerous? What if there are several bikes with these lights? (which is often the case) It’s not exactly safe to travel whilst not looking where one is going.

    Another point to note is that epilepsy is something that can be triggered suddenly in someone who has never shown any symptoms before. It’s very difficult for that person to avoid things that may trigger seizures when they don’t even know that they are prone to them. Imagine a scenario where a person has their first seizure whilst driving a car. Could be dangerous.

    The notion that people who know about their condition ‘try to avoid these things’ is also not practical. Where I experience cyclists with flashing lights is mostly on pavements which are shared cycle routes or from cyclists on the side of the road whilst I am walking on the pavements. Are you suggesting that epileptics cannot walk around the streets at night? I would have to give up work during the winter so that I didn’t encounter any cyclists on my way home. Sounds like discrimination against people with disabilities to me.

    One particularly bad experience that I had with cyclists was when a large group of around 100 cyclists (enough to form a decent peleton) staged a mass protest in the area that I live. It appeared to be some kind of ‘own the streets’ type protest held at the 6PM rush hour (obviously without the local authorities being informed about it) in the winter when it was dark. The cyclists occupied the entire road blocking the traffic and came riding towards me as I was walking home from work. Lots of them had bright flashing lights and it was incredibly painful. There was no way that I would have known about that in advance in order to take any necessary action to avoid it.

    Also many epileptics are in control of their condition and have been for many years. There are legal restrictions for safety reasons for people who have regular seizures or have had one in the last few years in terms of not being allowed to operate a motor vehicle and not being allowed to do certain jobs.
    These restrictions do not apply to someone who has previously had seizures but hasn’t had one for a number of years. By cycling with unnecessary flashing lights, you run the risk of triggering a seizure in someone who has not had one in many years and thus affecting that persons life for a considerable amount of time in the future.

    It’s not just epileptics who are inconvenienced by these lights, many pedestrians and drivers who share the same space as cyclists (often not at their own choice) have complained about the flashing lights.

    There is no proof that flashing lights are safer but there is proof that they can cause confusion, disorientation and discomfort.

    It doesn’t take much effort to switch to a fixed beam setting but it does cause a lot of problems for other people when a cyclist uses a flashing light.

    It’s all about consideration for other people.

    • James,

      While I’m sure that your comment is intended to protect people with epilepsy, I feel I must respond because I believe it has the opposite effect. First of all, here in the U.S., epilepsy is only considered to be a disability if it can’t be controlled with medication. In most cases, it is seen as an illness, a treatable illness.

      As you mentioned yourself, most people with epilepsy, including my own family members, can be treated successfully. Further, your experience as one person with epilepsy does not represent everyone with epilepsy. These are your own experiences, as one person, and your own opinions.

      The doctors I have worked with have been doing epilepsy research for many years. During that time, they have seen thousands of epileptic patients. While you may be unable to look away from a small flashing bicycle light, and may feel discomfort or disorientation from looking at it, many people with epilepsy do not, and they would be offended at your suggestion that they are unable to do so. Please be aware that many people with epilepsy do not consider themselves to be “disabled” and less capable of doing things than people without epilepsy.

      As for the danger of looking away from a flashing light while driving, people do this all the time when driving and cycling due to very bright automobile lights. I often ride my bike on rural roads where cars routinely use their high beams. Even at a distance, I am blinded by the light and cannot look straight ahead. To avoid crashing, I put my left hand over my eyes to reduce the glare, and look downwards so that the headlights are not shining directly into my eyes.

      Sometimes the driver notices me and turns down their headlights. Other times they do not. I have never crashed my bike because of the blinding headlights or from looking away from the road until I pass the car. The same is true when I drive my car. If someone is headed towards me with their high beams on and forgets to dim them, I look towards the side of the road so that I am not looking directly into the bright light. I have never crashed my car or even come close to having an accident from doing this.

      Your theory that people who have never had a seizure before might have one triggered by a flashing bicycle light is very farfetched. While it’s not impossible, it is so improbable that one would have a much greater chance of being struck by lightning than have this happen to them. Lightning is also dangerous, and it can kill people. So maybe we shouldn’t let anyone drive on the odd chance that they might be struck by lightning for the first time while driving and cause a serious accident.

      With respect to your assertion of “proof” about flashing lights causing confusion, disorientation and discomfort, I would say that if any exists, it is mostly anecdotal. One or two small research studies confirming this doesn’t prove anything. You have to test these things on large numbers of people for the results to have any meaning.

      There is anecdotal evidence that flashing lights are safer in that they attract attention to an approaching cyclist. I use a flashing light occasionally, in certain settings where I believe I might not be seen in time otherwise. In my own experience, drivers not only see me, but they give me more room and are less likely to cut me off when turning left than when I don’t use a flashing light. So, I have fewer problems with drivers when I use a flashing light. This enhances my safety.

      Now, the main reason I have written such a long comment is that I, and many of my friends and colleagues, have spent a lot of time advocating for people with epilepsy, particularly with respect to driving. Because of the type of arguments you have set forth, which paint epileptics as fragile, disabled people who might have a breakthrough seizure at any moment, many people around the world do not believe that anyone who has or had epilepsy should be allowed to operate a motor vehicle. It’s words like yours that keep people with epilepsy from driving.

      Just because someone has had seizures at some point in their life does not mean that a flashing bicycle light will trigger a seizure and cause them to lose their driver’s license. This will happen so rarely that it is not even worth considering. Other things such as sleep deprivation or acute stress are far more likely to trigger a seizure after one has been seizure-free for a prolonged period of time. These things can be monitored and avoided by people with a history of seizures to prevent a recurrence.

      One last thing I want to comment on is your obvious dislike for cyclists. Do you think that this bias might color your view of flashing bicycle lights? After all, if your theories are wrong, more cyclists could die on the roads as a result of not being visible to motorists. Does this worry you at all? Or are you only concerned that the small subset of people with epilepsy who might experience discomfort or seizures from the flashing lights be accommodated? In other words “consideration for other people” should mean consideration for all people, not just one group of people.

  3. amuletts says:

    I am a cyclist and a migraine sufferer. Like epilepsy migraine can be triggered by flashing lights. Migraine is described as the 3rd most common disease in the world.
    I’m not really sure of the safety provided by switching your light off every once in a while anyhow. I’ve used a color change light to attract more attention. (I look like a space ship)! I also wear a protective jacket. Basically I am saying there are alternatives to flashing lights. No one wants an unbearable throbbing migraine with vomiting, diarrhea, blurred vision and disorientation. Love cycling; hate migraine (and other photosensitive conditions).

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