In order to avoid the flat visuals commonly associated with split screen effects, two body doubles were used to allow the lead actor someone to physically interact with.
The time machines original design was only meant to be two doors on a hallway. But production designer Vincent de Felice presented the director with more then a dozen designs, includes this was which he doodled in the corner, because he thought the director wouldn't like it.
When the warehouse door opens, it couldn't be done remotely. Forcing first AD Cheyenne Smith to use the lead actor Samuel Dunning, to block the cameras view of her, so she could open the door then exit behind Sam as the camera dolly's forward.
In the shot where Tim Travers hand is visible in the foreground, and another Tim Travers( Samuel Dunning) is visible in the background. The foreground Tim's hand is actually the hand of director Stimson Snead.
The corpse being dragged out on the warehouse face down, is actually Director Stimson Snead.