Originally Posted by cyccommute

LEDs are very directional. From dead ahead they are extremely bright...sometimes too much so. From even a very shallow angle, their brightness drops off quickly. In cross traffic situations, cars approaching from the side may not see your light at all. That's generally not a good thing

There's a couple of ways to fix this. One is to mount the LED lights on your helmet. Since you tend to turn your head to look at the cars...and other stuff...approaching, your light will flash at them and get their attention. This is far better for getting the attention of drivers than putting a flashy to the front. The helmet light also illuminates stuff you are looking at like corners while you turn. Lots of bad stuff gets hidden in that dark corner.

The other way to fix this is to not use a light source that is so directional. Halogen and HID are omnidirectional...meaning they shine in every direction...and are usually mounted in a reflecting device to focus the light on the target. That's what the MR in halogen bulbs stands for...multireflective.

The same advice applies as to mounting however. Put one on your head. A helmet mounted light is far more useful than a bar mounted one.