The designers elevated the driver cabin so that it would be possible for passengers to walk underneath it when they coupled multiple trains together into a longer one. Sadly, it turned out the doors for the interlocking mechanism were very error prone so in the end they just welded them shut and you have to go around outside (at a station) if you want to move between trains sets.
There was also a telescoping gantry-like contraption that went across. I can see how that is quite fragile mechanically in a moving vehicle with vibrations and everything.