Lighting

Lighting on a motorcycle serves two safety functions. First it lets the rider see the road when it's dark. Second it lets other road users better see you in both the dark and the daytime. All motorcycles currently manufactured are required to have the headlight permanently on whenever the bike is running to increase visibility (conspicuity).

By adding lights to the bike you can further increase your conspicuity to other road users, but where should you put those lights? More lights on the front? More lights on the back? How do you decide.

Well, back in 1981 a comprehensive survey of accident statistics was published known as the Hurt Report (the primary author was Prof. Harry Hurt). Among the findings were the following:

Two-thirds of motorcycle-car crashes occurred when the car driver failed to see the approaching motorcycle

and

77% of collisions occurred in an arc of +/- 45 degrees from the front of the motorcycle. Accidents occurring from an arc of +/- 45 degrees from the rear of the bike amounted to only 5.5% of the total

I think the conclusion is clear that if you're only going to have extra lighting on one end of the bike, it should be on the front! Of course it doesn't hurt to also have additional tail and/or brake lights, but if your funds are limited, lights on the front of the bike may be more effective at increasing your visibility to other road users than lights on the back.

Though there have been few studies on the optimum positioning of additional lights, it has been suggested that additional lights (running lights) should be mounted in pairs, as far apart as possible. It's possible that widely spaced lights suggest a larger frontal area and make you look a little more like a car when seen from a distance. Drivers tend to see what they are looking for, so if they are looking for cars and you look more like a car, there's a better chance they will see you. That's the theory anyway.

Lights of a contrasting color to the headlight may also increase conspicuity. Obviously you have a limited color range from white to amber since in most states any other color lighting on the front of a vehicle is illegal (no blue or red lights for example). However within that range there's everything from a warm tungsten light (typical headlight) to cool blue-white "xenon" (and "LED") lights. Anything that's unusual (e.g. mixed color lighting) may tend to be noticed more.

So, for example, a pair of cool white LED running lights spaced widely apart would make a good addition to the single tungsten filament headlight which most bikes have. LED based lights are preferred for two reasons. First they draw less power then tungsten filament lights. Second LEDs last much longer than tungsten filament bulbs.

At the rear of the bike, a single bright red LED based brake light is probably the most effective additional lighting. If you can mount it high up (for example on a top box or luggage carrier), so much the better since that brings it closer to the eye level of following drivers.