Arrow Dynamics built ten suspended roller coasters, and Ninja is considered a suspended coaster because the cars are mounted under the track and are free to swing from side to side. Cars on inverted coasters are rigidly mounted under the track, but are not free to swing side to side. Arrow built ten suspended coasters, but never built an inverted coaster. The inverted coaster is much more common with nearly three dozen built by Bolliger and Mabillard, over a dozen built by Intamin, and over 40 "Suspended Looping Coasters" built by Vekoma. (Yes, I realize that Vekoma calls their inverted coasters "Suspended Looping Coasters,", but I am sticking with the industry-standard nomenclature.)
Under the center of each car is a circular guide-wheel that rides in a trough mounted in the station. This stops the car from swinging when riders climb in and out of the car. In the back right corner of each car is a smaller wheel that unlocks the restraints when pushed upward by a metal bar mounted in the station. The half-circle mounted behind that wheel is a foot pedal that can be used as a back-up to the automatic restraint locking and unlocking system.
©2016 Joel A. Rogers.