cycling in winter with daytime lighting

Daytime Lights: Magic Bullet Or Not?

Two recent tragic bicyclist deaths in Florida resulted in a local newspaper column extolling the importance of daytime running lights. Without going into detail about these tragedies, I’ll say one thing: It’s doubtful that either death would have been prevented by daytime running equipment for cycling

That’s the thing about tragedies and safety equipment. Whatever safety equipment you’re enamored of — daytime running lights, protective padding, helmets — it will help some times, but not others. But when you’re upset because a friend died, that kind of thought-chopping doesn’t come to mind.

Of this you can be sure: Safety equipment is an area where “always” and “never” don’t exist, and where emotional baggage leads all of us to want to cling to a magic solution.

As an expert witness in bicycle crash reconstruction cases,  I believe daytime running lights are usually superfluous. Yes, there are specific occasions where they do help. But they often are used as a makeshift solution for problems best solved by behavior change. If daytime running lights are offered as a do-it-all solution, they become grist for victim blaming when a cyclist was doing nothing wrong.

When To Light Up

Let’s start with the situations where daytime running lights do help. These would include fog, heavy rain, the sun low on the horizon, confusing lighting, and short sight distances on curvy roads.

Fog can reduce visibility to a very short distance. Where I live, in the hills of eastern Pennsylvania, the hilltops can be in the clouds and the valleys can be clear. Sometimes I may need daytime running lights — very bright ones at that — to be seen in the fog. But a half-mile later, I’m out of the fog, and visibility is good.

Some of the curviest country roads make a case for daytime running lights. Even so, if you measure the actual sight distance on a curvy country road, you’ll be surprised at how far it really is.  There’s plenty of space to slow down from curvy-road driving speed to cyclist speed. But there’s no harm in giving the overtaking motorist a wake-up call.

man cycling with daytime running lights

Scott Slingerland, executive director of Bethlehem, PA’s Coalition for Appropriate Transportation, demonstrates the effectiveness of daytime running lights earlier this month in Easton, PA.

view from rear of man cycling with daytime running lights

Scott is easy to see coming and going. But is this because of his lights?

Lane Position

It’s your lane position that affects how soon you’re seen, often more than any light can. This is especially true on curvy roads. If you’re hugging the curb on a curve to the right, you come into view later than a rider using a lane control position.

Dappled mottled light, on a tree-shaded road, makes a case for daytime running lights. The brain takes longer to assemble the picture of a bicyclist in such lighting conditions.behavior more important for cyclist safety than daytime running lights

Daytime running lights need to be bright enough to be conspicuous in daylight. If not, they’re no more effective than a rabbit’s foot. How often have you seen a bicycle light, in bad need of new batteries, blinking feebly — in broad daylight? I saw several on a recent trip to Philadelphia. A dim, poorly aimed daytime blinkie just sucks up the electricity to make the light even less effective at night when that rider absolutely needs it.

Brightness costs money. The least expensive bike lights (less than $10 for a front-and-rear set from a major discount retailer) are usually bright enough for nighttime use. But I wouldn’t bet on those lights being noticed on a sunny day. To be seen in daylight, you want a more powerful light. The taillights that have a strobe function (Portland Design Works Danger Zone and Planet Bike Superflash are two that come to mind) cost more than this. So do brighter headlights.

I recommend that you test daytime running lights in the situation when you might use them. Turn them on, take them outside, and see how they appear from 50 paces away. Do they jump out at you? Are you sure? Remember, you’re an alerted observer, and you are far more attentive to them than the people you want to see them. Those people are un-alerted observers.

When the Sun is Low: Your Shadow Points to the Danger

Does a daytime running light really solve the sun-low-on-the-horizon problem?

when the sun is low, your shadow points to the danger

While the world probably looks clear to this cyclist, his shadow points toward drivers on a high-speed arterial road who have the sun in their eyes – and may not see him as he violates their right-of-way

As we teach in CyclingSavvy, the sun low on the horizon can be a serious problem. Your shadow points in the direction of people who can’t see you. And in the class, we tell people to take a different route or to wait a few minutes for the lighting conditions to change.

The need to verify your lights’ adequacy is most especially true when the sun is low and casting glare. In that situation, you’re asking your daytime running lights to overpower the entire sun! If you do a good observation experiment — with several observers, please — take good notes and tell us what you saw. We’ll publish it. Bonus points if you take a good photo.

Blinded By The Light

What if your light is too bright? At a minimum, you annoy people. You distract drivers from their ongoing job of absorbing visual information and then going on to the next bit of visual information.

It’s a fad — a bad fad, in our opinion — to make emergency vehicle lighting so bright and so discordant that it’s difficult to look away from it. But look away you must, in order to focus on the path you need to travel. The driver needs to watch where she’s going, and watching the light display interferes with that.

Some of today’s lights are strobes, rather than light-emitting diodes. Are they too bright? In some situations, yes. For daytime running lights in pea-soup fog, probably not.

Remember, in normal lighting conditions, a cyclist in a black shirt is easy to see from 200 yards away. And all of us have an obligation to be looking when we drive.

Daytime running lights make you more visible, certainly. But if you were already visible, does making you more visible help? I don’t think so. You need to be relevant as well as visible. The nature of driving is that the driver discards most visual information. When he sees a bicyclist on the shoulder, his brain thinks, “That cyclist is out of my way, and he’s not a factor.” A blinking light is unlikely to change that thought process.Do daytime running lights make you more visible in court?

Any search engine will find you dozens of articles in which daytime running lights are praised as if they are mother’s milk. In those articles, people who don’t use daytime running lights are badmouthed. This is stunningly irresponsible, because it aids and abets victim blaming where it matters most — in court.

Imagine yourself, the victim of a motorist-at-fault car/bike collision. You were plainly visible. But the defense counsel brings out a stack of articles telling you what a jerk you were for not using daytime running lights. He asks you to read them aloud on the witness stand. Your emotions go south and your blood pressure skyrockets. After the first dozen articles, he calls for a break, and out in the hall, offers you $100 to settle the case then and there.

So. . . use daytime running lights mindfully. And promote them cautiously.

13 replies
  1. Geoff Hazel
    Geoff Hazel says:

    If I had a cycling savvy attorney, would he/she object to the introduction of those articles as “not expert testimony” ? And if the law doesn’t require daytime running lights, could that just end the discussion right there?

  2. Harold A. Karabell
    Harold A. Karabell says:

    It’s quite surprising to learn that daytime running lights are considered by so many self-described cycling safety experts to be so essential. Simply confining the discussion to “accessories” (and ignoring the even more important considerations of educated, lawful behavior on the roads), isn’t a high visibility riding jacket of much greater efficacy and necessity? Full disclosure: I’m hardly a disinterested commentator on the matter, since I always wear a high-visibility riding jacket/windbreaker but use daytime running lights only in the specific conditions enumerated in Mr. Schubert’s fine article.

    • John Brooking
      John Brooking says:

      That’s pretty much my practice as well. I’ll usually have my hi-viz windbreaker, except sometimes in August or September when the days are warm enough here in Maine to not want a jacket, and I only turn on my lights in daylight hours for dark skies, rain or fog.

      John’s last few paragraphs are a lot of the reason I don’t want to start running lights all day every day, nor promote that as necessary.

  3. Tim Potter
    Tim Potter says:

    Excellent article. Really gets deeper into the whole lighting topic that I’ve not read elsewhere. Raises some great points, however, one reason that I encourage DRLs is to make sure that we’re not overlooked by the increasing numbers of distracted drivers who, especially during daylight hours, are bombarded w/ visual distractions. There’s also the issue of the increasing numbers of aging drivers with visual impairments (or simply slower reacting eyes to changing light conditions) who continue to drive even though they really shouldn’t. I’ve almost been run over by at least one in a bright sunny day where I was riding in and out of dark shadows by overhead trees with good lane positioning. The drivers were obviously aged and not doing the typical honking, finger-flipping, etc. and looking straight ahead responsibly. So it dawned on me that they likely couldn’t make me out in the dark shadows having just driven out of bright conditions. My 2 cents, and yes, I’ll continue to encourage DRLs in my work and classes but add the caveats that you enlightened us to.

  4. Clint (retired LEO & CA Police Bike Patrol Instructor; CSI Candidate
    Clint (retired LEO & CA Police Bike Patrol Instructor; CSI Candidate says:

    Good thought-provoking article John! Like Karen during daytime, I always wear hi-viz apparel and at least a rear DRL taillight. BUT, it’s ALWAYS in combination with good, safe, legal and respectful “driver” behavior!

  5. Joe Bob
    Joe Bob says:

    I know as a driver that daytime running lights have alerted me to a cyclist before I probably would have noticed them otherwise. Also, on multi-use paths they help differentiate cyclists from pedestrians with enough distance to be able to make decisions on the path you would want to take. And for a lot of us that ride early or late it is a habit to turn them on before a ride.

  6. Josh
    Josh says:

    As a commuter, I leave my generator headlight and tail light on 24/7. Not because they’re useful 24/7, let alone essential, but because it’s the easiest way to make sure they’re running when they are useful.

    Recently, I upgraded my commuter to the Lumotec IQ-X, which adds a feature I’ve never had before on a bike light — in daylight, it automatically switches to a higher distribution of light for conspicuity, while at night it retains a sharp cutoff allowing me to see the road without creating excessive glare for oncoming traffic. No adjustment needed by the rider, and no need to switch through multiple modes to get the one I want.

  7. Eli Damon
    Eli Damon says:

    I agree with everything in the article. One other situation in which I would use a taillight during the day is when my route leads me though a tunnel.

  8. Frank Krygowski
    Frank Krygowski says:

    In my experience, most of the praise for bike DRLs takes the form “I could see him from way back there.” But even if a DRL gave somewhat earlier warning, that’s not usually valuable. A motorist needs to notice a bicyclist soon enough, period. As a motorist (including driving sag for invitational rides) I’ve never seen an incident where a light made a _significant_ difference. In fact, there have been countless times where I’ve thought “There’s a cyclist up ahead,” then much later thought “Oh – and he’s got a blinkie taillight.”

    And as if to corroborate that fact, I had a magazine whose back cover advertised the Bontrager Flare taillight. It laid on my coffee table for days, during which time I never read the ad, I just glanced and said “It’s a bicyclist being passed by a car.” I eventually asked myself “What are they advertising?” and realized they claimed the barely-visible taillight was supposed to be important!

    Another point: I’ve ridden with cyclists who have bought these talismans. One guy has three taillights, but all point upward at about a fifteen degree angle, shooting way over the head of any following motorist, but right into the eyes of a friend following on a bike. Please, if you’re going to mega-light, don’t blind your fellow riders.

  9. LesB
    LesB says:

    Technical error: A “strobe light” is ANY kind of light source that flashes at a fast rate. A “Light Emitting Diode (LED)” is a type of light source and can be operated to burn steadily or in a flashing mode.

    The rest of the article is just as wrong. I have never heard or read an opinion that DRL are the all that ends all. Of course. Nobody ever said that! Nor are nighttime running lights. Nor is any safety measure. But all help.

    I know from being a driver of a motor vehicle that the flashers give an early warning of a cyclist ahead. Lights at any time of day are not a sure-fire way to prevent accidents. No measure is, short of not going out on that ride. But everything safety that one can do will help. DRL help a lot. I’ve noticed that with bright forward flashers make drivers give more leeway.

    Many accidents happen because one driver “just didn’t see” the other car (or cyclist or pedestrian). Flashers mitigate that circumstance.

    Please, no one decline to use daytime flashers because of this misbegotten article. After all, it started out with a glaring technical error. Things just simply did not get better.

  10. John Forester
    John Forester says:

    American cycling policy is based entirely on the fear of same-direction motor traffic. That’s the way that Motordom designed it and government implemented it. Just so long as this policy continues (and I predict that it will continue), it is inevitable that the public will think that cycling is a dangerous activity and will demand protection from same-direction motor traffic, all implemented with the motorist-supremacy/cyclist-inferiority mindset. Since the assumptions behind that policy are contrary to known fact, it is inevitable that our cycling world will be filled with absurd suggestions about “cyclist safety”. We rules-of-the-road cyclists should hope that most of these would fail, but if any one of these shows either getting into law or “established safety information” we have to exert our effort to prevent its success.


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