If you want to get obsessively technical about it, there are no coasters without restraints. There are, however, some coasters and other rides with no active restraints such as Tig'rrr and virtually any log flume. Think about it. On Tig'rrr for instance, there is a seat, it has armrests on both sides, and it uses inline seating almost on the floor of the car, which makes standing difficult anyway. But there is no lap bar, no seat belt, nothing else we normally think of as a rider restraint. But the rider is still, in my opinion, restrained in the vehicle.
--Dave Althoff, Jr.