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Each section worked on its own from tunnel to tunnel. The cart is powered entirely by gravity at all times.
In total there are 11 cuts in the video, 7 between locations and 4 for slow motion footage. The jump section and the loop section were filmed twice, once in 30 fps and again in 120 fps, and the final video cuts from the normal speed footage to the slow motion footage for the duration of both the jump and the loop.
The cart worked reasonably well underwater and only fell off the pool track a few times. The main problem with the pool track was keeping the track connected and in place. A rock was attached to the end of the track in order to weigh it down.