Many flashlights have the "SOS" mode, in addition to fast flashing and solid. It is something like three long flashes, two short flashes each composed of 3 very fast flashes (or something like that--it's what seems to be on my flashlight). I find it a nice pattern because it's not so annoying as the fast flashing, and when it flashes it's on high, so very good for alerting pedestrians as I did today. Is it OK to use the SOS mode on a bike when there is no emergency? Likely no one pays attention to the pattern, especially since the bike is constantly moving instead of staying in the same place, but I just want to make sure it's acceptable.

Yeah, you can use it but why would you want to.
Seriously though, I've used an SOS mode on one of my drop-in torches coupled with an amber lens for rear-daytime alert use. It really does depend on the circuit though as some SOS ( modes ) on some torches are really slow, especially on the dash-dash-dash sequence.

Currently I use a custom Amber drop-in that has two very good flash modes; one is a nice constant slower flash and the other a series of quick strobe-like flashes followed by a one second pause ( and then repeats ) This is a real attention getter for day time use. Has memory and works great.

I would prefer something faster, but unfortunately the fast strobe on most flashlights is WAY too fast. I'd prefer something around 2 hz, but the choices seem to be SOS at < 1hz average and fast strobe at about 8 to 12 hz, which is just irritating for everyone.

It's illegal in most areas to falsely call out or signal distress. The reasons are obvious. That's said, I think it unlikely anybody is going to care or notice that you're signalling distress by flashing SOS, whether you are actually in distress or not.

I just wish light makers include a slow-flashing mode on most bike lights. The fast flashing is very annoying to both myself and others. This SOS mode emits strong light but slower, so that strong light stays for a second or two, which helps with both illuminating and alerting (mind you, it is much more effective in alerting pedestrians than ringing bells or horns: pedestrians can be deaf but rarely keep eyes shut). It also saves power relative to solid mode. Since no one (I hope) will be watching me all the time as I'm riding along, so it's not like flashing SOS mode at a fixed spot to attract attention and signal distress.

+1 to comments above
Use it on a rear red
Preferred for
Battery savings
Less irratating than strobe
IMO not a issue about being illegal
Prefer if light had slow strobe

Dinotte has a slow Flash.

Probably not a good idea to use the SOS mode when next to a large body of water. Some life jacket beacons flash SOS so boaters might think there's someone in the water who needs help. Don't think there's much chance of confusion otherwise.

I have a couple of lights that are supposed to signal SOS, but they all signal SO. So I'd be signaling indifference instead of distress.

LOL, that's actually the case perhaps with all the flashlights on this mode: SOSOSOS... instead of SOSSOSSOS...

I've got a flashlight that actually flashes SMSMSMSMSMS

I inadvertently selected the SOSOSO option this morning instead of the strobe today, and I'm sure I've done that before. I don't think anyone noticed, or cared.

Maybe the sorry fact is, nobody will care if any bicyclist is in real distress.

Why am I thinking of the first scene in Blazing Saddles?

the led mini Maglite does a true sos with a pause in between , it only puts out 77 lumens though

I see no reason not to use it. I doubt if most people even know what SOS is suppose to signify. If used on a moving bike I also doubt if anyone would actually see the whole sequence so really the point is moot.

The other day I noticed a rider that was using a couple bright white flashers on the rear of his bike. At first I thought someone riding on the wrong side of the road. Then when I got closer I saw he was going the same direction as me. After a moment of thought I decided that while it is not recommended, "What the hell"....it got the guy noticed a quarter mile down the road. Laughingly when I got right up on him I noticed he also had a small dime-store red blinkie which I could almost not see. Sometimes if you can't afford the more expensive bike gear you have to use what you have. Also funny in this whole story is that the guy passed a cop on the side of the road with radar ( which, thankfully did not get me ( or him..........this time ).

The SOS signal is still used. However Morse Code has been officially retired so the message is playing to a smaller and smaller set of folks everyday. The use of . . . _ _ _ . . . in my opinion should STILL be reserved for emergency situations.

I have used the sos for daytime cycling, usually along with a steady light. No one has said anything, and I have had cops in the other lane see it. If you stop at a light behind a car, tilt the light down.

The SOS mode on most flashlights is fairly slow. One exception is the KEYGOS M10, $20 on ebay. The SOS is fairly fast, making this a great daytime blinky, if you don't mind the large size and weight (26650 batts).

I have a Fenix that does that. It's a new kind of illiteracy!

One of the 18650 flashlights I bought from DX had an SOS mode, but it did

dit dit dit -pause- dah dah dah dah -pause- dit dit dit

... which is almost SOS, but not quite.