Duel’s ride system exists to solve Wardley’s belief that omnimovers remove any degree of surprise and consistency from dark rides, as inevitably someone at some point either sees the scene triggering ahead of them or sees it resetting, both of which are real mood killers.
In theory, with the right lighting, once you leave the station on Duel you should be able to make it most if not all the way around without actually seeing another vehicle, further adding to the mood as you suddenly feel much more alone. However, that effect is lost at several points these days.
The rolling loading system is used to get throughputs up and keep continually loading so that you get the capacity benefits of an omnimover but without the issue of trigger points around the ride.
I believe that Mack did sell one other ride system similar to Duel (I think it might be in Japan? I distinctly remember hearing someone had stumbled upon a second one.). However, compared to a lot of other similar transit systems on the market at the time it was very complex and quite costly (a single vehicle on Duel cost more than the average family car when it opened, and they bought 32 of them!).
Tomb Blaster is a strange ride system in general. I’ve never seen another one quite like it other than Journey Into Imagination at Epcot. The ride uses trains which are stopped and started within show scenes and the stations. Again, it goes some way to addressing the need of not having scenes reset in front of guests (albeit, it not as personal of an experience as Duel, as you’re sat in a train rather than single groups), but due to the fact the ride stops at several points (originally for the story to play out, today for you just to shoot targets) it probably wasn’t practical to attempt to rolling load it. You need the vehicles to move as one to maintain the timings.
