You've exhausted this part of the level.
There should be a door that will take you back to the main floor. You know the one where you started this part. Now, go back up the elevator you used before. Turn right and go into the control room. There should be three doors to this room. One is the door you come through. The next is the way out onto the catwalk. The last is where you want to go. If you found this room earlier, Kyle says something about wondering where the Tram car is.
Duct Tape is like the Force: it has Light Side and a Dark Side and it binds the galaxy together.