One thing I wonder about is the use of wide or double doors (2 people can use the door at once) in most PCCs, trolley buses (at least in the front), and Cal-Car Amtrak stock. It almost seems like that was an experiment that has died, with single-width doors being standard on all motor buses since the 1940s and on nearly all non-commuter rail equipment.

Is there something wrong with providing for 2-way traffic, or a double line of people boarding/alighting?