The color-coded key looted from Gore-Gore that unlocks any ochre-line engine car — the party's route to hijacking a train home.
The Ochre Line Engineer's Key is looted from the ManTauR Gore-Gore's corpse (along with 498 gold, Rev-Up Magic Hair Restoration, and the full ochre-line neighborhood map). It unlocks the sealed lead engine car of ochre-line trains — the party's answer to breaching an engine car without derailing (and thereby stranding) a whole line. But it's color-coded: it works only on ochre-line trains, not other lines.
Carl's refined plan is to steal such a key, breach a still-moving engine car, then use a fast looping train like the Nightmare-Express to leapfrog ahead and catch a train still running up the line — since a derailment only stops the trains behind it.
An engineer's key coded to the ochre line.
A line-locked key that is the party's cleaner route into an engine car and toward the stairwells.