A driver changing ends on 12 car trains 4 times per shift will be walking 1km before adding in the walks at start and end of shift.
I might be out of line here, but walking 1km is not any sort of distance, even for someone who is overweight (as a large proportion of the population are). If someone can’t easily walk 1km due to being overweight, then they need to have a chat with themsleves about their life choices.
People with injuries to hips / knees / ankles etc are of course another matter.