Hmm… The indictment mentions that normal engineering practice would include an “upstop”, which is apparently a wheel or other part of the vehicle that rides under the track [1] to prevent it from going airborne. In addition, it says the restraint should have been a “Class 5 restraint consisting of rigid overhead shoulder bars with a locking lap restraint”, which would effectively prevent the rider from going airborne. So it seems like if both of those things had been present, designed properly, and of course tested and maintained, that would provide a high degree of safety without needing to fully enclose the track.

[1] https://www.quora.com/How-do-roller-coasters-stay-on-the-tra...