I have decent lights (B&M Cyo Premium/Topline Plus). They are outstanding in the dark, but not so visible in bright sunlight.

Mine too. Second time I noticed a difference I figured I should continue using them and have been doing so for years.

By "IME" I meant what I see of other cyclists, regardless of what I'm driving. I think the longest underpasses around here are 6 lanes, but in the day there's usually plenty of light from the other side to see a silhouette. If you're riding through a "dive and climb" underpass YMMV. And though my lights are fairly recent (they tend to die after 3-4 years), they may be "sucky" by some standard.

• I wear bright shirts and helmets.
• My rear lights are very bright, always on and always blinking.
• My front lights are bright but are usually steady state.
• I have my head on a swivel and eyes on the mirror.
• I can yell really loud.

;o) -- In spite of all this, I love to ride!

European riders are advantaged by their carefully developed bicycle infrastructure and their more generally empathic cultures. We here in Murica are only in the beginning ---.

Joe

I won't ride, day or night, without my See.Sense Icon on the back. 190 lumens set to one LED solid and the other one pulsing. Far too many idiots on the road to risk running without it.

Lights won't protect you from an idiot. They won't. So why do we keep saying we run lights to keep us safe from idiots? Lights help the competent and courteous drivers (that remain the majority of drivers on the road) see you better, and thus do the right thing by you. That's why lights are useful. But they aren't really needed in the daytime. Cars have DRL because they have 90 watt alternators onboard that keep the 70 amp/h lead/acid storage battery charged at all times. A fluorescent green/yellow cycling jacket uses 0 amp/h and provides at least as much visibility as the commuter light set.

Just this week I learned that it has been proven that DRL don't really help cars stay all that safe! Why not? Because like a lot things safety related DRL was the wrong answer to a question no one asked. The two cars collided not because they couldn't see each other, but because either one or both of the drivers did not exhibit proper defensive driving technique. You MUST drive (ride) defensively to stay safe over the long term. Americans have a critical lack of the essential quality of humility that makes defensive driving or riding possible. In an accident situation the American goes for the horn! That's 1/10 of a second WASTED. You should have gone for the brakes instead in the scant fraction of a second you had to keep from becoming a C5 quadriplegic.

The car that right hooked you SAW you! S/he expected you to use your common sense and yield to 4500lb of car and driver! So do I. Flashing things and day-glo colors can only go so far to keep you healthy and alive. No matter how visible you are out there, motor vehicles will occasionally usurp your right of way, it is critical that your behavior in those situations is defensive first and foremost and afterwards as well. In a single week last week at least three individuals were shot dead AFTER near collisions. They would be alive today if they had just let it go. FWIW.

Agreed - on a sunny winter day, contrast between light and shadows is very strong. Without head/tail lights in the shade, a rider might as well be invisible. I'm adding a Light and Motion vis 360 helmet light kit to my safety arsenal after the holidays - when it comes to daytime lighters, the brighter-the-better.

let's not forget this aspect: the visibility thing isn't just about being seen, or even just about being seen early, it's also a screaming plea: "please don't kill me &/or please gimme a freakin' break, will ya?" almost like an Asian bow "please & thank you" from wiki: Bows are a required and expected part of any apology or expression of thanks in East Asia, especially Japan, Korea, and Taiwan.

I only run lights in low light or darkness. Rear blinks, front steady. I wear a bright colored shirt or jacket all the time. And if I know I'll be riding in the dark, I have suspender type reflective strips to wear over that.

I tried a front flashing once and it messed with my eyes so much I changed it back to steady. Riding home yesterday at dusk I saw another cyclist coming toward me with a bright strobe. Honestly it was kind of hard to tell it was a cyclist and I thought it was some sort of strobe in somebody's yard at first. The light was so bright you couldn't see him when it flashed and it was just dark enough outside that he was hard to see between flashes (or perhaps my eyes didn't adjust quickly enough).

Hub dynamo, + LED, I see no reason to Turn them off in the day.

As I write this, I am awaiting delivery of the Cygolite Metro 850 headlight that will complement the Cygolite HotShot 150 rear blinkie I bought last month. I have not used either one yet and will probably not start commuting again until around April of 2017, but I feel really good about upgrading my commuter with these very bright daytime lights.

I have no doubt at all that cyclists using blinking LED head and tail lights are much more visible during the day, especially when the rear is in a steady blink mode and the headlight is in what Cygolite calls "steady/pulse," which provides a steady beam for "see" light and an intermittent flash for "be seen/be noticed" light. This is how I will be running mine.

High-vis does almost nothing in bright sunny conditions, and absolutely zero in dark conditions. It helps in low contrast overcast day conditions, however. I run flashing lights at all times, on flash mode during the day. From a mile away, my flashing rear lights are ABSOLUTELY more visible than anything else. And as was mentioned earlier, during high contrast conditions such as bright sunlight with intermittent shadows like from tree, lights may be the ONLY thing making you visible when you pass from a sunlit area into a shaded area, from the POV of an observer in the sunlit area.

But as far as being visible and noticed goes, riding away from the edge of the road did far more for me than any sort of lighting device has ever done.

Again, particularly on bright sunny winter days, drivers' eyes take time to adjust to shadows - I want very bright lights when I am riding in those shadows.

Jeez, I was only exercising my God-given 2nd Amendment rights. After all, a side-arm is more effective than the souvenir baseball bat that I usually carry.

... see, I am not doubting that a flashing rear light is visible from that distance... I am wondering why you think you need to be visible from that distance...

How would you know? Hopefully, you will never have to find out, but... ... what if not being anywhere near a potential hit from the rear is the wiser course of action...???... I mean... if you are riding out from the edge of the road...say in the right hand tire track... or if you are really b@d***, lane center, ... well that Buick Century being driven by the 88 year old stroke survivor that is closing on your six at 75mph better see you, right?, and the sooner the better, because the reaction time of that driver is 2 seconds vs the usual 0.25 second!

But what if you are over on the shoulder? Hell, even the fog stripe?! WHOOOOSH sure sounds a lot better to my ears than BLAMMO, SPLAT ... OMG... ... EWWW. In the first scenario, dude never even saw you... never knew you were there... cruised right past you... but, no worries, you were quite safe, because you weren't in his way! In situations where you have to be in the way, speeds are usually much lower. Sometimes less than 1mph. Plenty of time to see even the cheapest POC blinky sold. You don't need to be seen from a mile, you just need to be seen. It really is dependent on application. Runway strobes are visible from 20 miles so that aircraft on final approach at 170 mph can do what they need to do. The DOT mandates that blinkies be visible at 200' and I suspect their estimates are conservative. A mile is over 5000'. FWIW.

^^^^ MA dot states front lights need to be able to seen from 500' That is a really long way. I parked my bike with lights on and paced it out. Brighter is safer, IMHO. The downside is? Nothing.

I concur.

If bike is moving, at least my two obnoxious flashing lights in the front and one in the rear are on. In addiction to my two magnetic powered bike lights.

After the sunset, two heavy artillery headlights (nicknamed "Fire Balls") enter the game, together with obnoxious helmet front and rear lights, second rear blinky, two panniers-mounted rear red blinkies, and standard front and rear LED lights. In addition to hi-viz vest, which, by the way, is mandatory by the law here in Italy, after the sunset.

I once read an interesting article on the matter, here: What an RAF pilot can teach us about being safe on the road ;)

I live in Los Angeles and have been hit by cars twice(within 2 weeks of eachother actually...)I ride 7 days a week and during the daytime, no matter what the weather, I have my head and tail on their most annoying strobe setting.

Depends on where I ride and what season of the year it is I sometimes run rear light during the day on the fastest blink mode.
Where I live it's more or less bright all summer long so I don't carry any lights with me during the summer.

Must be the moth effect.

Dynamo hub, LED lights, no switch. If the front wheel is turning, the lights are on.

Does it help? Who knows. Most likely daytime lights don't help much of the time, but if they have helped a driver see me one time, in all the years I've had them, then they've been worth the effort. Every little bit helps.

For daytime - flashing mode is sometimes even better than steady.

Dusk and dawn (low sun) is the time of day when I'd use lights, even if the visibility is OK.

When the visibility is low, front light is better left on steady, while the rear one is OK in blinking mode as well. Since rear one works for drivers approaching straigh on from behind = lots of time to spot, while the front one should be seen in the split second a driver pulling in from a side road takes to look for traffic and notice the bicycle. If that split second is the light's "off" phase - bad luck.

Oh gee I don't know, maybe because I like to give myself the best chances possible of motorists knowing for sure that I'm there, and giving them plenty of time to react as necessary, and perhaps pulling their heads out of their arses for a moment at least until they pass me.

Unlike some people I stay aware of my surroundings at all times, including directly behind me. I monitor motorists approaching from behind in my lane, and I can easily observe them either changing lanes to pass, or slowing down as necessary until they can change lanes. In nearly 4 years of riding LANE CENTER by default, there has only been ONE TIME where I felt the need to take evasive action due to a motorist coming up fast behind me and not moving over. He was trying to pass me while coming up a blind hill, with another motorist oncoming. I could see in my mirror that he wasn't slowing down much, or moving over much, so I made a quick lateral move to the right edge as he barely squeezed by.

When I rode at the edge by default, MANY cars would buzz pass me closely. Were they going to hit me or not? I couldn't really tell, and I would flinch every time I got a close pass. Riding lane center, it almost never happens. When it comes to close buzz passes and close calls, less is better than more.

These "take the lane" arguments are always right... and always wrong. It really depends on current situation, road conditions, relative speed (car vs your bike) and drivers habits.

For example, in my country, I tossed the mirror off my bike. Cars would always, that is 9 out of 10, approach as if they'll run me over, turning at the last second. Even when there's no traffic coming from the other direction and they can use a whole other lane to pass me. That's the way drivers are used to driving here.

Also, Friday and Saturday night, with lots of drunk drivers, staying in the middle of the road is the last thing I'd recommend.

Low visibility, with high speed difference and little room for overtaking is a situation where taking the lane is almost as bad as staying to the right side.

Another example: I see a car coming from the opposite direction and there's a car behind me. I'd move to the right - there's room to pass. If there's a truck, or a van coming from either side, I'd take the lane and signal the approaching vehicle to slow down and wait for a better opportunity.

So there's no real rule of thumb IMO.

I am a fan of head/tail lights 24/7 but not a fan of weaponized headlights ever.

Do what you like. In the last 4 years I've ridden all around Desoto county in northwest Mississippi just south of Memphis, in and around Memphis city proper, plus surrounding suburbs, and in West Memphis, Arkansas. Also Atlanta, GA, Destin and Miramar Beach in Florida, and St. Louis, MO. Different times of day or night. Different seasons. Different weather conditions. If there are no bike lanes and the lane is too narrow to share, or if the bike lane contains dangerous hazards, then I use the full lane by default. Problems have been very, VERY rare.

But I also run lights at all times as well. Flashing during daylight, steady or pulsating during dusk/night/dawn.