Peter Fox wrote:

Following on from 's message. . .

Driving home last night I overtook a cyclist with what from about 100m
away I thought was a very dim constant rear light. As I overtook him I
saw it was a Cateye LD600 on the chasing mode where each LED lights up
in turn but there is only one LED on at any time. So from the
perspective of a driver this mode would appear to be useless. IE only 1
fifth of the light put out compared to either the constant mode where
all LEDs are lit or the flashing mode where all LEDs flash
simultaneously. Plus from a distance the chasing mode loses the
flashing effect.

Actually when 'all LEDs are on' they are switched. In the dark wave the
light in front of you and you won't see a constant blur. (But that's
not very relevant to the discussion.)

LED lights are usually powered from dry cells which go slowly from being
100% to empty. (Unlike rechargeables, which is why they are used on the
rear where you can't keep an eye on them.) Naturally you only
batteries when necessary so one day you'll think to yourself 'the lights
are a little feeble - to be replaced!' At that point a sequencing
flasher is borderline. (Note that typically one LED will have the same
brightness _each_ as five together - which is not the same experience as
most people have had with filament bulbs, where you get two half-bright
bulbs instead of one fully bright one. So 5 LEDs give plenty more light
than 1.)

A single flasher is probably not much good in built-up areas but if
bright will be fine in the country. Obviously the reason for using
fewer LEDs is extended battery life. This is where you can't make rules
but need to get people to ask themselves "can I be seen in the current
circumstances?".

FWIW I use five flashing about town except at dusk or wet when I use all
and in the country when it is properly dark a single sequencing flasher.

LEDs are also generally awful when run from NiMH cells. The slightly
lower voltage gives *half* the brightness (I measured it with a light
meter). Stick to alkalines, or, if financially possible, the Energizer
lithium cells which are the full 1.5V and have a more or less flat
discharge curve. If you need another incentive, they're very light in
weight.