Bright daylight: front off, flashing rear.
Overcast, foggy, dusk, etc.: flashing front and rear.
Dark: steady front, flashing rear.
(steady rear if riding with someone close behind me).
Originally Posted by
vane171
Basically, in poor visibility conditions, you should ride your bike defensively as if you were invisible to car drivers, which means you don't really need the front light, except if its so dark that you need to see where the side of the road is. But such riding is only for commuters who often have no choice, makes no sense for sport riding to go out in poor visibility conditions, never mind dark.
That would be true only if it was midsummer the whole year round, with 20 hours of daylight. For those who are working 9 to 5 and still want to get some rides done on weekdays during the winter, there is no choice, commuter or not.
And what about endurance rides that may take 24 hours or more?