You climb up
right foot first. The door has automatic closing action which kicks back to prevent unwanted opening.
If you ascend the railing into this locomotive left foot first, you will reach the top and be unable to simultaneously depress the door handle and enter the cab.
Nobody has ever fallen from the Amtrak genesis pictured, or at least never been reported or blamed the company. Even though they never tell you this in training. You just figure it out yourself, and then always remember that you "get on and off with the right foot!"