I think the ideal light might depend on where you are. I ride mostly in the Big City. It's insanely dense and disorderly but speeds are fairly low. The legal limit is now 25 mph, and I hope it goes down further. It is going down in many cities. Also, cyclists are seen in most parts of the City, so drivers are used to us whether they like our presence or not.

I use a dynamo-powered headlight made in Germany, and German law forbids flashing lights on bicycles, for better or worse. German law also mandates that the beam has a sharp cutoff to prevent blinding people. I aim it carefully so the beam does not point up. Because of the design of the beam, it is very sharp and focused so it seems brighter than it really is. I notice people noticing it. When I wiggle my handlebars to say I'm coming, people seem aware of my presence. And by the way, the handlebar wiggle is a technique I recommend, for instance when someone is about to walk in front of you or a driver might be about to cut you off.

I do use a flashing taillight in the City, and I'm not categorically opposed to flashing lights. I just haven't found a flashing headlight to be necessary.

And yeah, don't be the jerk with the overpowered light in people's eyes. "It gets people to notice me" is not a great approach. If you punch someone in the face, they'll notice you but that doesn't make it a good idea.

I don't really get the flashing headlight thing. In two-way traffic, the traffic coming from behind certainly will not see it. Oncoming traffic is separated laterally by a lane of traffic. While they will probably see and notice it, perhaps more so than they would a non-flashing light, to what effect is it in real terms? In my mind, there is no advantage to it, and since I find it annoying, I assume others do as well. My Garmin has a low-brightness non-flashing mode, which is what I use. I am happy to report that in the last 65 years of cycling, I have never been killed, not even once. Many of those years, I was without a headlight in the daytime. 60, IIRC.

I don't like flashing red rear lights, either. It's not that I have any light sensitivity; I simply find them annoying. I do understand that they may have a marginal functional advantage over a non-flashing light.

Based on the statistics with which I'm most familiar, the #2 and #3 highest motor vehicle crash risks for legally-operating cyclists in urban areas are left turns from oncoming drivers across the rider's path and drivers on side streets and driveways pulling out into the rider's path (#1 is same-direction right turns).

The hypothesis seems to be that the increased conspicuity created by a flashing headlight can reduce these crash risks. And to my knowledge, we have lots of "anecdata" but not much hard data. But the huge reduction in cost in a bright flashing front light since the LED revolution has made many more people willing to see if it helps them.

A cycling industry writer several years ago decried what he described as the "conspicuity arms race" on city streets with varying-brightness motorcycle headlamps, mandated motor vehicle daytime running lights, and bike-mounted flashers. He feared that drivers would either tune it all out or only look for lights, not road users.

OK, I can see the argument for that.

/rant mode on/
I'm also a motorcyclist, another thing that I've never been killed doing, not even once. One thing I have learned from that activity (it was derived from cycling before I started riding motorcycles in 1972) is that any car in the left turn lane IS ABSOLUTELY GOING TO TURN IN FRONT OF OR INTO ME. If I let that happen, it is my fault. You see, the consequences of a car vs bike or motorcycle collision are far too serious for me to think in any other way. I will tell myself that I was at fault for anything that happens to me that was even remotely foreseeable. I don't want to be 'dead right'. Thus, I assume responsibility for my own safety, whether on a bike where my maximum speed is maybe 25 mph or on my motorcycle where I might be going two to three times that fast. Frankly, I don't believe that people who can't see a cyclist, headlight or no, are going to see a flashing headlight. I really don't.

How did I learn this? I was riding downhill on PCH when I was 15 years old, mebbe doing 20mph. A police cruiser made a left turn in front of me to go into a pizza joint. I braked hard but t-boned him, flew off my bike and over the hood of his car, did a tuck and roll, came up right, and ran smack into a telephone pole. It was at this point that I knew I was invincible, but I didn't ever want that to happen again.

He was nice; he gave me $5 to 'fix my bike', put it in the trunk of his cruiser, and gave me a ride home. He even apologized. The best thing he gave me was an everlasting distrust of anyone who is in a left-turn lane or in a driveway pulling into traffic. Upon reflection, I decided that the only person who would watch out for me was me, the only person responsible for my safety was me, and the person at fault for any injury to me was me.

Thinking this way has saved my ass many times.
/rant mode off/

I still have a motorcycle endorsement on my drivers license, but it's been decades since I rode a motorcycle regularly. That said, I still clearly recall several times I had to perform an emergency stop or lay the motorbike down to avoid a cranially-inverted left turner.

I still watch for this threat while riding my bicycles, but the lower approach speeds helps a bit in crash avoidance.

Please don't take this the wrong way; I know I am about to be a dick.

If you got to the point where you had to take extreme measures, then you weren't thinking the way I do. When I come to the point where there is a person in a left-turn pocket or in a dividing zone, I would already be slowing and maneuvering to a safer ground. From the instant I saw that condition, I'd be expecting to be turned into (hamburger).

In line with something noglider* mentioned, I was on Highway 89 in Arizona, headed into northern Arizona. It is long, straight, and desolate. Most people drive it fast. It is a two-lane road. I rode next to the centerline; my riding partner next to the shoulder. When an oncoming car got within a half mile, I'd wiggle-waggle, riding in a bit of a zig-zag, then I'd slide over next to the shoulder. From this vantage, both of us could see the oncoming car. I don't know if everyone noticed the wiggle-waggle and then the movement to the right, but many of the drivers reacted by sliding to their right, making more room for all of us. I don't know if they did so because they were safety-conscious or if they thought I might be an unhinged ball bearing thrower. But I think the wiggle-waggle is not a bad idea.

This was me proactively taking charge of my safety, so I stood less of a chance of getting my butt run over or off the road because a driver didn't see me.

I believe that side-to-side motion grabs attention; an oncoming light, blinking or not, is background.

*Als ich diesen Benutzernamen zum ersten Mal sah, dachte ich, da stünde „nogilder“.

In a rural area, a driver can have greater leeway for lateral positioning. In an urban environment, however, it can be difficult to track all potential conflicting movements or threats. Taking a lane position to minimize them where practical can indeed reduce the risk, but not eliminate the risk.

I will digress off-topic for one important exception: a rider can practically eliminate just about all risk from a suddenly opening car door by simply not riding in its swept width. This is feasible on most roadways with on-street parking. In locations where such a lane position might increase exposure to overtaking traffic, it's my understanding that the dooring risk significantly outweighs the overtaking risk, except under unusually high overtaking speeds or volumes. Some riders feel comfortable riding adjacent to parked vehicles, apparently assuming that they can detect occupancy and react in time to an opening door. However, tinted windows, larger or taller vehicles, and ubiquitous headrests make that detection task impractical at cycling speeds, plus a door can go from closed from fully open in half a second, while the rider is still in the perception region of the perception-reaction response.

You make some very valid observations. There was a time when, as a rider, you could look at a parked car and watch for tailpipe emissions, shaking tailpipe, the engine made noise you could hear, you could see the driver because there were no tints or headrests. Power steering made squealy pig noises. There were no brodozers except, maybe, the shop teacher's genuine Power Wagon. You could see where the driver was looking; almost every driver would look down at the door handle and shove the door with their shoulder when opening it. In short, there were far more visual clues.

I got doored once. The thing about being doored is that the bicycle stops immediately, while you keep going for just a little bit. When hit from behind, at least you keep going. I have only been hit once from behind. The first thing that ran through my head was "Save the bike!" and I ejected the bike out from under me so it could make a safe landing on the grassy boulevard strip.

T-boned a car, doored a car, and got clipped before the age of 18. Nary a scratch since then. Learn early and learn well, because too soon old, too late smart.

Just a quick note - some of the higher end German dyno powered lights have a sensor so that in daytime it can light up different LEDs that are more noticable in daytime. A friend of mine had his Luxos U (now discontinued) light on in day time, it was bright enough that it was easily seen, even without flashing. Photo below:



Yes he should have had a helmet on, but he only took a quick spin around the state park campground.

Id be curious to know what you [OP] decide on.

I can't understand the reason for the many inimical replies. We are here for the same purpose. Safety! We don't want to blind anybody with our flashing lights. Presently, I attached a flashlight to my handlebars. I would say it flashes at about 200 -300 lumens. I don't know whether a dedicated bike would be better.

If your goal is visibility, dedicated bike lights have a wider beam than a compact flashlight mounted on your handlebars. Off axis and side view conspicuity will be better with the bike specific light. Not sure if you have any Garmin mounts but the Raveman FR### series is one example. I use the FR300.

Now use a Knog Cobber rear, which leads me to their front version. It can be mounted directly to handle bar. Cobber Reflex Front it has a wide 330° beam at 350 lumens, and many flash options. It is USB-C rechargeable.

Another issue with flashlights used for bicycle headlight duty is that many off-the-shelf flashlights have battery mountings that may be less-secure under vibration, causing flickering and outages on bumps and rough pavement. Speaking as someone who has experimented with inexpensive Costco flashlights as bicycle headlights for over a decade.

With my aging eyes, for night use I personally like having a tight bright spot beam on the roadway sufficiently in front of me to reveal roadway imperfections, with a much wider cone of less-intense light also emitted which is typically more than sufficient to illuminate signs and make other road users aware of my presence. I've used bicycle-specific lights with a wide bright beam, and I prefer the bright on roadway / not as bright elsewhere pattern. And a lot of off-the-shelf flashlights provide exactly that pattern.

Some of the complaints about overly-bright daytime flashers may be because the user places the brightest beam directly ahead instead of down toward the roadway (which isn't needed for a daytime light, but then results in that searing straight-ahead beam).

P.S. I solved the vibration issue on off-the-shelf flashlights on the bike by replacing the internal batteries with a cork with two screws in it, a small drilled hole in the barrel, lots of NYK anti-corrosion compound, and an external dry cell pack (4 x NiMH AA) which provide inexpensive all-night run times.

I know my comments aren't intended to be inimical, but more along these lines:
1. Increasing conspicuity may or may not reduce crash risk - we just don't know for certain.
2. Riding behaviors can affect crash risk more than increasing conspicuity.
3. We don't know all the second-order and third-order effects of increasing use of daytime lights across the road user fleet.

Will it hurt? Probably not. Will it help? It's not completely clear. But at least the option to do so is readily available and inexpensive.

There is a phenomenon that I don't have the ken to name, but it has to do with intensity. An LED producing 500 lumens is a very small aperture with that much light coming out of it. It can be blinding simply due to the intensity, or lumens per square yahtzi. If you compare that to a vintage Cibie Oscar, you could have 500 lumens coming out of one of those beasts, and it would look very dim. (I use the Oscars for illustrative purposes; most people would load them up with bulbs capable of 2000 lumens. You'd probably need to find a 35W H1 to deliver only 500 lumens.)

So many of the vehicles today have the same amount of lumens coming out of their headlamps as the old 7" round lamps had, but now that light is coming from a point source, be it a projector or an LED, that is much smaller than the 7" parabolic reflector that projected the light produced from a tungsten filament in a halogen atmosphere. These lights are annoyingly bright simply due to the intensity., Fortunately, the plastic headlight covers fog up in a couple of years, and they become much less annoying to look at.

Luminous energy: total amount of light thrown by a light source (per unit of time)
Luminance: light per unit area thrown by a light source

And this doesn't even include illuminance or anything else in the IES Handbook...

RCMoeur, Thank you!

I ride mostly on rural roads during the day and currently using a Bontrager Ion headlight for daytime use. Can be seen from a good distance and lasts a good 6 hours in daytime flash mode. It is very small and weighs next to nothing. I believe there is a new version out with a USB-C port, which should be an improvement.

I think part of the issue is the color of the light. The old sealed beam 7 inch car lamps had a lower Kelvin rating than the halogen lights that came after them, and then the LED lights can have a higher Kelvin rating than the halogen bulbs. Those higher Kelvin rating lights I find are more irritating.

A couple years ago I bought a new headlamp (for my head when camping, not biking). I had a choice which LED I wanted, a soft white with lower Kelvin rating or the higher intense Kelvin rated LED. I chose the softer white rating.

This is interesting. You sound like you aimed to make the light pleasant. But you won't be looking at the light as you use it, so it's not for you, it's for others. Do you think a pleasant color makes you more visible or less? Or is pleasantness independent of visibility? I think a somewhat unpleasant color might enhance safety though probably little, if at all.

The soft white is closer to the color temperature of the morning sun, and I find I see better (or perhaps more comfortably) with soft white. We have a chandelier in the stairwell that had halogen bulbs in it; I always found it irritating. A bulb went out, and I wanted to find LED replacements, but could only find them in something like 4700K. I bought them, and then went and got some photographic gel sheets to make some capsules to change the color of the emitted light.

It was immensely satisfying to accomplish this most "from the sublime to the ridiculous" task.

Seems as though periodically through out my more than fifty years of driving the type of lighting in the headlamps changes. And I find the new color of them a tad annoying. However in all cases.... I've gotten use to them.

It's still the drivers and cyclist that have their lights aimed directly into my eyes that are really annoying. And it matters not what the color or Kelvin is.

I assume you are saying that in response to my comment:
..
I just do not like bright bluish artificial lighting, I find it harsh. And I think that it is easier to see things that don't have that high Kelvin rating kind of light. Perhaps that blueish color makes it harder to see colors when it is closer to an edge in the color spectrum? There is a reason that a lot of indoor lights are described as "soft white".

My mother was a commercial artist. For work, she had a fluorescent light with two different color bulbs in it to provide more even lighting at her work table over a wider color spectrum.

Remember when all computer monitors only showed text, they had either green or amber screens. (TRS 80 computers were gray, but I think they were the only outlier.) The green and amber colors are closer to the middle of the color spectrum, your eyes would see better with less fatigue with colors that were not on one of the extremes of the color spectrum.

Tourist in MSN thanks for the explanation. It makes sense to me, about something I don't know much of.

The Xerox 16/8 had a white-on-black screen, the white was quite comfortable to read, no horrible blue tinge.
And of course the Sinclair ZX80 znd 81 used the b&w telly.