After agreeing to figure out a way to accomplish the massive stunt, Corbould’s crew eventually developed a large, remote-controlled piston to be placed under the truck. Ensuring the safety of the driver, Jim Wilky, was of critical importance, so Corbould’s men reinforced the driver’s seat with several steel bars to protect and hold Wilky in place during the 180-degree flip. During early tests, the piston successfully flipped the truck—remarkably in the right fashion. Corbould quoted, “I couldn’t believe my eyes…it had to go over straight, and it literally deviated off course by no more than six inches.”
The location of the truck flip in the film was a little tricky. Corbould noted, “The road Chris[topher Nolan] chose to do it was right in the middle of the banking district, plus underneath the road there were underground vaults for the banks…there were only two spots over this half mile stretch of road that we could actually do the gag.”
There was, however, one minor special effect needed to complete the scene. The Cinematographer for the film, Wally Pfister, (with whom Nolan collaborates on each of his films) stated, “The only visual effect involved in that scene was to remove the ram that they had built inside the truck that actually catapulted it.”
Because of the gravity of this scene, Christopher Nolan used several cameras to capture the stunt. He noted, “We covered it from I think seven different angles---4 IMAX cameras, 2 Vista Vision ones, a 35…I actually don’t like to use a lot of multi-cam setups, but doing a stunt that is not repeatable like this, you really have to cover yourself and make sure you’ve got it from all angles.”
In the final cut of the film, Nolan used two angles of the truck: a camera positioned on a separate vehicle moving along with the eighteen wheeler, and a camera located inside a cop car that was moving directly toward the truck. Nolan stated, “Much to our surprise we found this to be one of the most effective angles.”
Written by Anthony Watkins
SOURCE
The Dark Knight Blu-Ray disc
BELOW are three screenshots of the truck flip sequence. In the middle picture, you can see the piston that flipped the truck. (It's positioned at the bottom right corner, just in front of the yellow taxi cab). In the third screenshot, it is more clearly seen as it stands out in the smoke. This piston was digitally removed during post-production. (only special effect used in the sequence)