Hi,

Looking for opinions:

Any "real" advantage for a rectangular twilight geometry over the more typical round ones ?

Thanks,
B.

I never thought about it. But the bulbs are all round -- and even if the cases or lenses are of different shapes, tbey probably all look the same from a distance.

no advantage to either that I can see. Just choose battery or chargeable whichever fits you best

unless they're shooting laser beams, there's enough dispersion to make any differences insignificant at more the 5ft away. Brightness is what counts. i suggest the round one for flashing the rectangle for steady red. Two is at least twice as good, maybe more.

My two (okay,25 cents). If you are going to ride in traffic, as in commuting, then choose the light that has better side visibility. I prefer multi-LED lights with at least one "bulb" pointing off to each side. The next best set-up is to have a "deep" enough red plastic cowl to glow when seen from the sides.

If it's a question of esthetics, then it depends on how the bike looks, or the visual theme of the bike.

I agree with the last two posters: one light on steady beam, one flasher, and position them as far apart as possible -- e.g., one on a seatstay and one on the seatpost. Make sure at least one of the lights has side visibility. Shapes of the lights' cases or lenses won't matter.

Visibility above any other consideration, with multiple flash patterns. I personally like the light bar variant - all my blinky lights are Cygolight Hot Rods. Row of extremely bright LED's, about 2". Seven (?) blinking patterns from basic strobe to "Be seen from the Space Station" mode. Mounted properly they are visible from a long way off - I mount them on the left side seat stay and on the right fork blade. Mounting that way angles them up slightly and puts them directly in the view of an approaching motorist.

Brightness.
USB (or similar) rechargeable
Long battery life off a charge.
Easy on-switch, preferably that can be actuated with gloves on.
Easy to mount and dismount, and transferable between bikes.
Adaptable to different seat post/seat stay/handlebar/stem diameters and shapes.
Price.

Shape of the light is only considered after all the above. If at all.

You have 2 tailllights?

Round taillights are faster - see Ferrari, Corvette, Bugatti Veyron, etc. But you have to have them in pairs.

Red - tail light, white - headlight... All well and good to have cars coming up behind you see the blinky, but what about cars pulling onto the road or turning left across your lane? Always best to cover both front and back.

I have a solid and a blinky on the roadbike but just a blinky on the MTB. I also have white LED headlights that I can blink during daylight hours and switch to solid when it gets dark. All are rechargeable which is the only way to go today.

Separation between two or more lights is more important than the size or shape. On a bike it's seldom practical to install motor vehicle type lights -- too bulky and heavy, and they need too much power.

I few years ago I noticed that cyclists were much more visible, day and night, when they used two headlights and taillights, or mounted the second lights on their helmets. And helmets tend to be visible above the roof lines of most cars, while bike mounted lights can be obscured in traffic. Separation of lights helps with quickly estimating distance, direction and speed, whether a cyclist is approaching or receding.

So I started doing that. I've actually heard drivers and passengers slow down as they were passing and tell me the extra lights made it much easier to see me.

The next best thing we can do for visibility is mount lights that enhance our visibility from the sides. Wheel mounted LEDs are great for that. They really pop against cluttered backgrounds but aren't so bright that they're annoying and don't mess with the vision of fellow cyclists. (Reminds me, I need to put those back on my hybrid errand/commuter bike. I took 'em off a damaged wheel and never got around to remounting them on the new wheels.)

Drivers judge distance based on changes in apparent width.

Busch und Muller toplight line plus:
https://swhs.home.xs4all.nl/fiets/te.../index_en.html

Reflectors are good! none of your tail lights will ever be brighter than their headlights. This isn't saying don't run tail lights, it's just saying reflectors are important too. So if all you run is a light then run a light that is married to a reflector.

I am too lazy to go find the link. however there was a study or something that said reflectors that resembled a person was best. So legs arms, body. Which means ankle straps that reflect, reflectors on arms, and torso are all a good thing!

My take on it from driving. Blinking lights are hard to gauge distance on. Or how fast I am approaching them. Thus, you really want a solid light, to go with your blinking light. or a solid reflector to go with your blinking light.
Blinking lights are good, especially ones with patterns, because if someones attention drifts, the blink will re grab their attention.

I don't see how shape alters any of this, Except for the shape of a human body. jacket, vest, sleeves legs etc.... even if it's just an outline.


Edit: what really grabbed my attention one night while driving a car was the reflector of a guard rail, that was randomly blinking. It slowed me way down like from 55 to 30 ish !!! Still confused it wasn't until the next day, in daylight, I saw that someone had put up miniature flags. POW flags. that little 4x6 inch flag flapping in the wind was flapping in front of that guard rail deflector. In the dark I could only assume it was a person/animal on the road. I'll also assume that most driver would ignore this or never see it. So go all out if riding at night!