Bicycle lights have been around a long time, starting with decades-old generator-powered lights, and slowly progressing to AA-battery powered beams. Problem was, the lights weren't very dependable and they didn't work that well.
The AA-battery powered bike lights cast a small halo of light, not much more than a couple of bike lengths ahead in your path. More often than not, the batteries were dead in the garage before a ride. Generator-powered, or dynamo-powered lights, don't offer much more power than AA-batteries—that is, if the finicky system is in working order (who plans time to work on their bike lights before a ride?).
How times have changed over the past decade.
More cars, more congestion, more commuters riding before and after daylight hours, and the new sport of night mountain bike riding all helped to create a great demand for high-performance lights.
Companies sprang into action designing and testing bigger and better lighting systems that would enable night riders to actually see where they were riding, at any speed. Not only that, but the new lights were powerful enough that oncoming cars could see cyclists in the distance, too. The goal was to build the most efficient lights with the highest capacity battery at the lowest possible weight.
Riding Safety With Lights
No matter how bright your light, you're not guaranteed safe passage in a world of motor vehicles, so keep in mind three key points inherent to cycling with lights:
1. Light pollution. Unless you are lucky enough to live far from any fast food restaurants, your light will likely "get lost" in the melee of other lights that a city street produces. Motorcycles have the same issue—one beam, no matter how bright, just isn't visible enough for all the cars to see.
2. Getting lost in the dusk syndrome. This occurs in the hour or so before sunset when you can still see quite well and might not feel lights are necessary, but when vehicles have a particularly tough time picking a cyclist out of a busy background of competing images, and when it isn't quite dark enough for reflective clothing or stickers to shine brightly in cars' lights. At dusk it is especially important, perhaps more so than after dark, to turn on your lights, and rear flasher, to give cars every chance to see you.
3. Rear flashers are a must. What about the cars you can't see? A simple red LED flasher can be had for a few dollars and a couple of AA batteries. With a run time of up to 40 hours, it makes you exponentially more visible to cars coming from behind. If you have the option of using a flash or steady red light mode, go for the flash—it's makes it easier for cars to pick you out.
A note about using "front" LED lights, the white or green front flashers: White LEDs are much less efficient than the red ones used for rear LED lights, so they are much dimmer, and thus not a good replacement for a front headlight.Search for a cycling event