I think that "low speed vehicle" reference is made to cover an emerging class of vehicles that are limited to 20 - 25 mph. These may include NEV's or Neighborhood Electric Vehicles. The distinction is made because the requirements for airbags, side-intrusion protection, and other crash-worthiness features are dropped. They are not "street legal", but occupy a niche between a golf cart and an automobile. They do have to be equipped with" headlamps, stop lamps, turn signal lamps, tail lamps, reflex reflectors, parking brakes, rearview mirrors, windshields, seat belts, and vehicle identification numbers" according to NHTSA. They are not intended for freeway or highway use, but rather for "short trips for shopping, social and recreational purposes primarily within retirement or other planned communities with golf courses". They may be gasoline or electric powered, and some may even have a "low range" that further limits speed so that they may be used safely on a golf course.
Edit: According to NHTSA, one of the reasons golf carts don't require seatbelts is that it was initially believed you were safer leaping out of the vehicle than remaining inside in the event of a rollover. I'll bet more than a few people who were tossed overboard when the driver made a sudden turn might argue with that.
I followed one of these LSV/glorified golf carts home from the store a couple of years ago, after which a little online research on that vehicle ultimately brought me to Elio Motors . . . . and here.