At this moment, as you are discussing this in the space between cars, Phina continues in her workshop to tinker, and Utes is back in the team's car you hear a noise. A sort of loud
WHUMP sound. This is followed briefly by a cloud of black smoke that suddenly overtakes the tunnel, and then passes as the train speeds along. You all hear this sound, even over the loud clacking and chugging of the train as it continues down the track ceaselessly.
The raucous sounds coming from the soldier's car even go quiet as they all seem to have heard the noise as well. The sounds of the speeding train resumes as before.
What do you all do?
OOC:
As for train setup the main engine was up front. Followed by a small car carrying coal. This is apparently used to fuel whatever machinations power this thing. After that is the soldier car, and there is no door on the other side of the soldier's car, as there is nothing out there to get between the cars.
You would need to climb along the outside of the train to get up to any areas in front of the soldier's car.