Vancouver has one of the best mass transit systems in the world, but I do not miss the crowded trains that happen during peak times. I propose special ‘Overflow’ train cars that sit at the front and back of a train, increasing passenger capacity. This creates a longer train that extends beyond the length of existing platforms.
These Overflow cars have no exterior doors, so they cannot be accessed directly from train platforms. Passengers would board the train normally, then have the option to move to an Overflow car at either end of the train.
Thanks to the on-board alert system, passengers are notified of upcoming stops by digital signage and a voice over the intercom. This ensures passengers who are sitting in an Overflow car can make their way to an adjoining train before their stop. I would also add some sequential lights to point the way to the exit:
I would recommend just one Overflow car at both ends of a train, any more than that and it would be a bit of a trek when boarding or exiting a train. If additional Overflow cars are needed, I would designate them for passengers going to the very end of the line, which has a longer stop time.
As for the safety of an Overflow car, there would be an emergency exit at the front of the car, along with eject-able glass panes throughout.