How often do you check if the battery-powered rear light of your bike still works? Once when you start to ride. Once for every time you get too close to a cop. Once for every time a car gets too close to you. And once for each degree of paranoia.

Run an optical fibre* from the steering column along the frame all the way to the rear light and mount it so that its end can "see" the light. As long as the light works a small red dot at the other end will indicate that it does. And you may stop to wonder if this car driver did not see you or if he is just an asshole. He is indeed an asshole.

-------------

* How come that Firefox's spell checker does not know "fibre" but "fiber"?
-- Toto Anders, Dec 13 2014

Car Light Self-Check Car_20Light_20Self-Check
Seems similar [lurch, Dec 14 2014]

Or you could just look down.

I almost always have 2 independent rear lights. Reduces the chance of going dark by <mumble> percent.
-- pocmloc, Dec 13 2014


You could bake this in a few minutes with a TOSlink cable, which are very cheap.

It's hardly a halfbaked idea, though; too simple and practical.

// How come that Firefox's spell checker does not know "fibre" but "fiber" ? //

Because Americans don't speak the language very well, dear boy.
-- 8th of 7, Dec 13 2014


// It's hardly a halfbaked idea, though; too simple and practical. //

If my simple and practical ideas are not to be found out in the wild, doesn't that mean they have to be half-baked? O.k., I will try this one and get back to you and tell why it did not work.
-- Toto Anders, Dec 14 2014


I look out for the reflection of my rear light in shop windows or shiny cars as I pass them.
-- hippo, Dec 14 2014


What's wrong with "simple and practicable", exactly like all of my ideas aren't.

NB you need to load the appropriate dictionary for the spell-checker in firefox, default is usually US English. I'm still waiting for the Linear B one to come out.
-- not_morrison_rm, Dec 14 2014


@[hippo] // reflection of my rear light in shop windows or shiny cars//

Nice idea, except there are no shiny cars nor shop windows but only woods, hills and rain, where I bike at night - in the countryside.

@[not_morrison_rm] // I'm still waiting for the Linear B one to come out //

Bislama is missing from the list, too.
-- Toto Anders, Dec 14 2014


If there are no cars, you don't need to check the rear light.
-- pocmloc, Dec 14 2014


//Bislama is missing// Nope - I saw the video footage of when they found him.
-- MaxwellBuchanan, Dec 14 2014


And none of them said "You are Mr X and I claim my five quid".
-- not_morrison_rm, Dec 14 2014


// If there are no cars, you don't need to check the rear light. //

We were talking about *shiny* cars.
-- Toto Anders, Dec 14 2014


I know, but my statement is true nonetheless, by its own internal logic.
-- pocmloc, Dec 14 2014


// I know, but my statement is true nonetheless, by its own internal logic. //

This is not about true statements but about a rear light indicator - which is a true statement in itself.

Also, if there are no cars, there still might be buses, motorcycles and even other cyclists - their overtaking me is just a hypothetical possibility, but has nevertheless to be taken into account. It could be them needing the indicator.
-- Toto Anders, Dec 14 2014


Hmm, you appear to be correct.

The front lamp on my vintage bike has a little nib of clear plastic, integral to the lens cover, sticking up above the chrome-plated rim of the lamp housing. In fact I remember an uncle who drove a Rover P6, it had the same feature on its front sidelights.
-- pocmloc, Dec 14 2014


// The front lamp on my vintage bike has a little nib of clear plastic, //

Of course you could check by just looking at the rear light. The thing about checking the rear light while riding is that you are not willing to turn your head on a sore and stiff neck when you just found the perfect body inclination to get less wind and rain down your collar. You just want to look straight ahead and think of the hot shower at home. And follow the red dot.
-- Toto Anders, Dec 14 2014


Technology could also be used to determine the status of your frig light. Does it really go off ?
-- popbottle, Dec 15 2014


There's a light for that??
-- MaxwellBuchanan, Dec 15 2014


I tried it. One problem is the limited angle for light entering and leaving the fibre. You can mount it so that one end points exactly to the rear light and the other is visible on the handle bar. But slight position changes of the rear mount or the rider will make you fear that you just lost your tail light. So it is probably not so assuring as I thought.

My next attempt will be to mount a 2nd mirror by which I can see the reflection of the rear light on the frame.
-- Toto Anders, Dec 17 2014


Quantum theory suggests that the light is only on when someone looks at it.
-- hippo, Dec 17 2014


// Quantum theory suggests that the light is only on when someone looks at it //

But it also suggests the light can be on when nobody is looking as well.

Chaos theory would suggest that the light is never on and we simply perceive it's state to be whatever we wish it to be.
-- Canuck, Dec 17 2014


[Toto], what fibre are you using? Even the thickest communication fibre will be much too thin for this. You can get really thick (~1mm) plastic light guides which have a much better acceptance angle and carry a lot more light over short distances.

I once used one for checking the LED on a timelapse camera without having to go outside - it worked fairly well. Another thing you can do, using a magnifying glass and a vice, focus sunlight into one end and carry the other end into a dark room. Most entertaining.
-- mitxela, Dec 21 2014


A camera! Much better than a light guide or a fibre. Just rig up a mini video cam, broadcasting via a cellphone network to a videostream you can download onto a handlebar-mounted smartphone. That way, your friends and family can also make sure your rear lamp is working!
-- pocmloc, Dec 21 2014


// [Toto], what fibre are you using? Even the thickest communication fibre will be much too thin for this. You can get really thick (~1mm) plastic light guides which have a much better acceptance angle and carry a lot more light over short distances. //

That's exactly what I use: a 1 mm plastic string. Still the angle is not wide enough. Maybe I should try to sandpaper both ends to a half-globe.

//A camera! Much better than a light guide or a fibre. //

Aw, come on! Now you're poking fun at me (which I just cannot understand, given the beauty and health of my original idea). But why stop halfway? I also could use a camera drone flying behind the bike with an automatic infrared sensor control so that it doesn't need to be steered. I just would have to change batteries every five minutes or so.
-- Toto Anders, Dec 22 2014


Have a dynamo on the rear wheel, powering a laser which shines onto the drone's solar cells. Perhaps microwaves would be more effective.
-- pocmloc, Dec 22 2014


Shirley the light doesn't actually need to be on the back of the bike, just pointing backwards? Fit the tail light to the end of the handlebars, you should be able to see it all the time then.
-- bs0u0155, Dec 22 2014


// Fit the tail light to the end of the handlebars //

A nice idea, only the lights would dazzle the driver. In a pitch dark night with no other light sources even the white rim of the front light can be quite annoying. But you're right: the rear light could be mounted somewhere where it's easier for the driver to view, e.g. on the driver's ankle.
-- Toto Anders, Dec 22 2014


//somewhere where it's easier for the driver to view//

Not a good idea - unless it's on the rearmost part of the bike, it risks being obscured by the rider, or by parts of the bike (from some angles).

I very much enjoy yelling "Get some fucking lights!" at unilluminated cyclists as I pass them in my car. A partially-obscured but functioning rear light spoils my fun.
-- MaxwellBuchanan, Dec 28 2014



random, halfbakery