The opening scenes are a metaphor for the trajectory of the plot of the film.- the speed of the train wheels, the scream of the whistle, the roar of the engine and the flames convey a sense of dangerous passion. What is more, we are watching man and machine working together, each mutually dependent. As the engine is driven by fire, so the men need their cigarettes. They communicate with body language and unintelligible sounds, human beasts in fact. This is significantly different from Chaplin's Modern Times which portrays mankind as a prisoner of the machine. The train passes through tunnels, alluding to dark passages in the narrative. Arriving at last at Le Havre, music is added to the soundtrack. It has the grandeur which evokes a sense of achievement. Gabin checks his watch as if to confirm they have arrived on time or maybe beaten a record. As the train slows, so does the music. We have arrived and it is good.
These scenes do not necessarily signal a film noir but on reading the plot, you will find that we are deep in noir country. It is reminiscent of Double Indemnity and you can't get more noir than that.