Reflectors require being struck by sufficient light at an angle pretty much, but not entirely, head-on to the reflector. Unfortunately, when you get in some of the rural areas and are coming from a side road or driveway ( backing out ), there's not enough light from a vehicle's headlights or backup lights, to illuminate a reflector on a bicycle that's 100 feet away and coming at 15 or 20 mph. No reflector I'm aware of will do any good in a situation such as this, especially when backup lights are the only illumination to the rear at night. When I need to back out of our driveway at night, the radio is off and the front windows are down in order to try and hear any possible noise from a bike or rider coming down the road without lights, only reflectors on the bike. This situation always scares the hell out of me, but there are some riders in the area that don't wish to be detected on their bikes at night for other reasons than being legal and staying safe.