Here is a link to the Federal Regulations:
https://www.law.cornell.edu/cfr/text/49/393.26
(d) Use of additional retroreflective surfaces. Additional retroreflective surfaces may be used in conjunction with, but not in lieu of the reflex reflectors required in subpart B of part 393, and the...
Yeah, that article (and the paper it is based on) is terribly misleading. Like one of the earlier posters, I drive a BMW i3. I bought it for driving to and from work (which I haven't done much since then!). Using my charger at home, I get the equivalent of better than 100 miles per gallon...