Reflectors

The Louisiana law requires reflectors and lights:

Every bicycle when in use at nighttime shall be equipped with a lamp on the front which shall emit a white light visible from a distance of at least five (5) hundred feet tot eh front and with a red reflector on the rear and a reflector on each side facing outward at the right angle to the bicycle frame, all of a type approved by the department which shall be visible from all distances within six (6) hundred feet to one hundred feet to the rear when directly in front of lawful lower beams of headlamps on a motor vehicle. A lamp emitting a red light visible from a distance of five (5) hundred feet to the rear may be used in addition to the red reflector. 

After December 31, 1974 no person shall sell or offer for sale any bicycle unless such a bicycle is equipped with at least one red reflector on the rear and one reflector on each side as required by this section. This section shall not apply to bicycles while engaged in sanctioned competition races.

But note especially the last sentence .

Laws vary state to state.  But getting clear information is tough. I just looked up what the law is in Pennsylvania.  I found two references.  One stated (w/r/t side reflectors) that the operator of a "pedalcycle" (there's a great term) "may" supplement the required front light (between sunset and sunrise), the other stated that side reflectors "shall" be used - the former indicating it to be optional and the latter to be required. 

The best part is that the side reflectors in both references are supposed to be amber, yet all the bikes I have ever bought in PA (9 or 10, counting the kids' bikes) have had white reflectors on the wheels, which technically would either be unnecessary or illegal (depending on whether I "may" or I "shall" use them).

On a practical basis, using reflectors does not really enhance safety during daytime hours, as there is no headlight to reflect off them.  What I do, in practice, is leave reflectors on the kids' bikes, so I don't have to worry about them forgetting to use lights at dusk. But I removed them from my bikes.  I keep a red flasher on the back of the seat bags of each bike to turn on at dusk, and I have several small lights that slip easily onto the front of a bike if I expect to cut it close coming home on a ride at dusk.  I try not to ride at nighttime, since the more powerful lights are (a)expensive and (b)hard to keep topped off without causing battery problems (at least in my experience).

Of course, a relatively cheap solution could be to use a Sure Fire flashlight with a bungee attachment to the bike or helmet - those things give a ton of light!