A typical CPSC reflector provides only 1.7 square inches of directly exposed surface area and 1 square inch of surface angled to one side under optimum viewing conditions. The cyclist is better off replacing this rear reflector with a larger one from an automotive store. Note that an amber reflector is 2.5 times as bright as a red reflector under the same headlight illumination. By law, a red reflector is required, but adding an amber reflector to the red one isn't a bad idea. With this combination, you'll be over ten times brighter than with just one CPSC reflector.
Reflectors are very sensitive to mounting location and orientation.
Reflectors on the frame should be mount low to reflect the lights of other vehicles sooner. The face of the reflector should be perpendicular to the ground. If the rear reflector is where it may be sprayed by mud from the tire, clean it often. These lamps will last many hours on a pair of disposible batteries. Some extra-bright tail lamps, such as the NiteRider Tail Lamp, run off of the same rechargeable battery used for the headlamp.