And what of darkness?… accident stats show that [being hit from behind] is unlikely. Far more collisions occur when a car turns in front of a bike—which means that bikes need headlights more than they need taillights. As for reflectors and reflective clothing, they only show when you're directly in the beams, so they won't prevent as many accidents as lights and bright colors such as yellow or light green (but not red, which the eye doesn't easily see in the dark).

Bluish-white LEDs arrived on the scene a few years ago, but the original red LED color is still the brightest. This makes small, battery-powered LED "blinkies" great as taillights, but marginal as headlights. A better choice is a halogen system. For city riding, it's more important to point it up, where it shines in drivers' eyes, so they see you, rather than down onto the road, which is already illuminated by streetlights and house lights. Look for something that puts out at least ten watts.