2 Tailights Better Than One?
 

I currently have a Blackburn Mars 4.0 and a old Superflash. I'm not sure which to use or should I use both? The Mars 4.0 is brighter and I was thinking of putting it on solid red and superflash on flash?

2 is better than 1 if they get along well and there's no jealousy. Wait, what? Yes. People should see you better, which is the purpose, with 2 lights.

Use both in case one fail. If you wear a helmet mount one on the back of your helmet. I did an experiment one time with my parter having one tailight on the seat post and one on the helmet. Both were identical light (pbsf). I drove a tall pickup truck and followed. From a distant I noticed the tail light on the seat post. When I was closer and slightly back, I saw mostly the helmet pbsf.

Yeah, redundancy is a good thing. You don't see many one-engined airliners ;)

I like the idea of putting one on your helmet if it works out. It'll show over the top of some passenger cars in traffic. Oh, and I'd have them both flash... longer battery life, plus they differentiate you from all the steady-red lights in the scene.

Attention - attention - that's what you want - put five lights on if you can afford it.

Two is about right. Leave one (the dimmer one) on all the time, put the other in a flash mode. Leaving a tail light on flash all the time can mess with a driver's depth perception, so leaving one on constantly helps alleviate that.

Two is better. There's a couple of common failure modes, battery runs down and blinkie shorts out in the wet. With two blinkies, you've got a good chance to notice a dying battery and replace it before it leaves you in the dark. From two manufacturers, you double your chances one of them knows how to make a waterproof light.

... and unlike your headlight, you usually don't notice until the end of your ride that your taillight stopped working. So two is very much a good idea.

Yeah, like other people said if it's not a horrible amount of trouble to mount both, two is better -
1. With one on steady and the other on blinking you can get the best of both worlds - one blinking which catches attention and identifies you as a bike to drivers, the other on steady which makes you much easier to track where you are.
2. If one fails people can still see the other one. The problem with the tail light is once you start riding, if it stops working you don't notice - it's behind you, you can't see it. I've arrived home before to find that the batteries in the light died, or a battery got jiggled loose (though I either permanently fix it or get a different light then) and I never noticed during the ride.

I really cannot relate to this urban legend, any more than I can relate to the idea that blinking lights make drunk people run into me. Maybe it's just that I'm extra-specially awesome, but I have no inherent problem getting approximate range on a blinkie in flashing mode. And there's no risk of it being overlooked as something else, such as a stoplight in the distance. Sign me up for 100% flashing.

That's the way I personally see it myself in my car - the bikes that are the easiest to track and the least annoying (to be clear, I also find bikes that I don't realize are bikes until I'm close annoying, which I like the blinking light as well to keep track of) are bikes with one blinking light and one on steady. It's not a "big theory", it's something I see myself.

I also did not warn of "catastrophy" without 2 lights, just said it was easier and makes the bike easier to track in traffic.

The idea that blinking lights attract drunks is supposed by research to some degree, though what the research finds is somewhat more complicated than that.

Flashing seems to be more popular in the US, and solid-on seems to be more popular in Europe -- even to the point of being mandated by law in some places.

I'd say do whatever you want. If you have two lights, you're not likely to go wrong with any permutation -- two flashing, one flashing and one solid or both solid.

One advantage of flashing is that the batteries generally last a lot longer, so the light becomes more reliable, if you want to take that into consideration. Personally, I also like how a flashing light screams "bike!" where a solid light could mean a lot of different things.

I think of my own traffic and the #1 job is not to be "tracked," it's simply to succeed in being noticed. Just a quick sample, got work to do here...


Which would you rather have here, one more steady red light to add to the collection of 20 steady red lights? or two strobing ones?



Or this ride (skip to about 6m 10sec in for the segment in question, or watch the whole thing to see me get pwned by Mother Nature):

#t=367s
Yeah, now you see why I'm packin' the DiNotte 300R around :D

If flashing mode sends the message that there's something ahead that's not a car, that trumps "trackability" any day in my opinion. If I want to provide range cues, multiple lights with physical separation provide divergence cues, e.g. a helmet light and a bike-mounted light.

I've ridden the highways for decades while observing overtaking traffic in my helmet mirror. My observation is that the more blinkage is going on, the more likely the traffic will change to the other lane on a divided highway at significant range, and that there is not the slightest trend for people to drift towards me. And my favorite highway is a pretty high likelihood of having drinkers, being the highway south out of the city AND leading to a major state university.

No one asked that question. All the responses so far have mentioned using 2 lights, one blinking and one steady.

As for what I would want to use in those traffic conditions, to be honest I would say "my car". There's definitely a limit for me where traffic is to crazy to bike in it.

None of these lights are steady-burn either:


I don't find that hard to "track" in the sense of where it is, approximately how far away it is, or what its headng is relative to mine. The key message is not "I am 200 meters away, plus or minus 20," it's simply "hey motorist, you're gaining on something fast, and it's not a car, give it space," with the corrolary of "those blinkie-lights generally mean it's a bicyclist, plan accordingly."

When the refrain of the motorists changes from "I didn't see him" to "I could not judge his precise range from behind, officer," I'll start worrying about range instead of just getting noticed.

I agree with mechBgon's philosophy on the steady/flashing argument. Not only does it make sense to me.....it saves on batteries too.

And something I've always wondered about the moth effect with the drunk driving.....if there's something to it you would think there would be a lot of those posts that hold the signs that have a yellow llight that flashes (to warn of a stop sign at a major intersection or a traffic light intersection ahead) would be hit right and left. They are flashing and in place 24/7.

The difference is that you're biking down a lowish traffic 2 lane highway where people have plenty of room to pull into the other lane. Being bright annoying and hard to figure out where you are works effectively (though annoyingly) when cars have plenty of room to get around you because they pull into the other lane.

When there is no other lane to pull into, this tactic isn't nearly as effective, because the cars behind you don't have anywhere else to do so they generally just pass you anyways. And since they don't know exactly where you are, well they aren't going to risk hitting another car headon over it, they just pull past you - something from your videos that you also do not appear to have to deal with as you appear to ride on either a 6 foot wide shoulder or on a road with no shoulder in which case you have to take the lane.

I simply prefer one steady, one flashing. When cars are going to be trying to skim by besides me anyways, which are they are going to do on a 2 lane road, I'd prefer they know where I am and not leave them guessing. I'm sure either one will work though, and either approach is better than not realizing that one of your rear blinkies went out and you don't have any light behind you.

This is a scary thought process to me. With no shoulder on a two way road with only two lanes the best method is to take the lane far enough to where the car needs to be in the other lane to pass. As you say they don't want to risk a head on with another car.....so they will have to wait until they can pass safely (just like with a car in front of them). That's WHY you take the lane.

And I'm not buying the "steady" argument. I WANT somebody to be annoyed enough to stay very clear of me.....not be able to gauge a distance well enough to get as close as they can and then "skim by". I think the likelihood of someone taking the other lane before they get to a point where distance is even relevant goes up when bright lights are flashing at them from the rear of my bike. I would think it far more important to ensure you have a steady light in front for when they merge back into your lane.

If there were a problem with them knowing where I were, I'd surely be dead by now, based on the fact I ride much more than just primo divided highway. Example:


I'm not saying it's worthless for the overtaking traffic to have a depth cue, but let's face it: having the light run steady isn't going to fix the fact that it's still a point-source of light with no appreciable width or height. If you want to fix that, you add more lights and now you have divergence cues. Also, if you follow a rider with a common blinkie such as a PBSF or Mars 4, it's not like there's big dead spots in the flash pattern. The PBSF switches between its main and secondary LEDs to provide a near-nonstop effective light, the Mars 4 just flashes quite fast. I can't imagine "losing track" of the cyclist in the milliseconds that separate the flashes.

BTW, the strobe shown in that video is the most "aggressive" taillight I've ever used, the Nova BULL. It looks like an emergency-vehicle strobe because it IS an emergency-vehicle strobe. It's gotten unsolicited praise, and nothing else, from motorists who either want to know where to get one, or to tell me I was easy to see from a distance. Annoying, praiseworthy, whatever... I guess it depends on the viewer.

One blinking, one steady. If both are blinking, and they are both "off" at the same moment, you are invisible , even if it's just for 1/5th of a second, you are momentarily invisible.

Also, I have seen LED tail lights on other bicycles, while I was driving my car, and I have good depth perception, but with the blinking light and no steady light (to focus on) , it is hard to tell where the bike is going. I glance ahead to see if there is oncoming traffic, and I glance back to look at the bike, but the "Blink" is OFF, and I can't see the bike at all.

Again, one blinking , one steady, and a third light on the helmet (blinking by day, steady at night).

I'm not going to get further into the "safety" argument, I've been on the forum for a while and it's not like we're going to come to some huge agreement.

The things that nearly everyone agrees on are that -
1. No doubt it's safer to have a rear blinky that none
2. Two rear blinkies are better than one because you have a backup in case one stops working - and because if one does stop working you don't know because the light is behind you
3. You're more visible as a bike if at least one of them is blinking.

The only other thing I know for sure is that as a driver, I prefer bikes with the 1 blinking + 1 steady approach. Second is a blinking light. I don't like a purely steady light as it's easy to get lost among a lot of lights, and obviously I really don't like no lights at all. I feel like steady + blinking is the right blend between visible and obnoxious, when I'm driving. However there are no absolutes - when driving through downtown everything is so lit up tons of blinking doesn't really bother me either. I also might feel differently if I was biking alongside high speed unlit roads, but I generally just don't have to bike along them.

For whatever reason, I also find rear lights on the backs of helmets to be the kind of thing I don't notice until I get really close, regardless of whether they're blinking or not. I'm not entirely sure why that is, except that I've had it happen again and again - maybe it's up higher and I'm not scanning for lights at the level, or maybe it's because they're never as bright as tail lights. The only thing I would definitely say is don't use only a helmet mounted rear light, put at least one light around seat / car headlight level.

To be fair - years back I saw some really terrible blinking patterns - anything with a long "off" in it's pattern is total crap. My dad has one from like 5 years ago, actually, and he puts it on that it it drives me crazy, the "off" is like half a second.

But - as much as I theoretically would like to agree with you, with most modern rear lights I haven't had a problem. They seem to be "on-on-off" now, and at a rate that's so fast that...well I'm just speaking from personal experience, but you can't really miss seeing them, they're on/off cycle is so short you can't look past it while it's off. I dunno...just what I've seen.

I use 2 PBSFs mounted on the rack. On flash, they are very noticeable, and the backup is there when the batteries die on the other. I have a helmet light on the front, but don't really want or need an extra light up top for the rear. If I was riding in heavy traffic, a helmet blinky would come in handy, but would be a third light, not second.

I would say 'Yes' IF....you can still get on your bike without trouble, after having raised the seatpost and put the two lights on the seatpost.

I did that at one point, but started to experience pain in my hips from the raised seatpost accommodating two rear lights. So I had to go back to one. Now I have one flasher on the seatpost, on my back, and on my helmet.

Anyway, That was my experience.

If you can do, definitely do it.

Nobody should be adjusting the fit of their bicycle simply to add a light -- there's always other places to mount the needed lights.

Fit the bike properly, and then if there's space on the seat tube, you can mount a light or two there. If not, there's always other options.