More than you would think. The reflectors are not so much there there for nighttime use anyhow, there are there to meet gov't regs and are a good thing anyway. Still there is no law I really know of (and I WILL be corrected) that says you can't toss them in the trash with the do not remove under penalty of law tag on your pillow and men in suits won't hogtie you and force you to push good eating habits in public service annoucements on late night TV.

I use those 1941 Columbia reproduction split red rear reflectors on mine anyhow, right near the bottom of the fender. They fade to near amber in the first place. If I give one to somebody else they usually get added small yellow/ambers near the split red and the one on the seat stays if it was there as well as the front plus any spoke-mounted ones are added or replaced as needed. THAT was for my nurse practitioner when I rebuilt a green 60s Hawthorne internal 3-speed as a single-speed with coaster brake and wider rims/tires. SHE takes good care of me so I wasn't messing around and if you want to see it go to You Tube and look up user steadfastcoward or 'Tempest The Grey Bike Grows Up' for Part 3 (Her Friends) and Il Ciclo Verde.

And to answer the original question, I've seen reflective tape on many bikes. It's easy to do yourself and you can put it where you think the most help is required as well.

I can't hurt to have an bright apple green front fork either, like Tempest does.