On Jan 24, 1:44*pm, Neil Williams wrote:
What do you mean by "traps" here?

Here is a photo which hopefully will illustrate. It's an older train,
but the principle remains.

http://world.nycsubway.org/perl/show?42183

Notice the front door in the corner of the train. Underneath are the
steps, and there is a metal plank "the trap" above them. At this
station, it is a low platform, and the trap would be raised at this
station.


This show shows another view of the doors, traps, steps.
http://world.nycsubway.org/perl/show?52861


Also, on all the older SEPTA trains, the vestibule doubles as the
engineer's cab and the trap becomes the floor.

On SEPTA, the downtown terminals and some busy stations are high
platforms, as are newly refurbished stations. But other stations are
low platform.

NJT has converted many of its stations to high platform, but low
platform remain.

On LIRR and Metro North, they decided to convert most of their
electric zone stations to high platform in the late 1960s so the
incoming Metropolitan/ Cosmopolitan cars wouldn't need traps at all
and be high platform only.


On US railroads, one problem with high platforms is that certain
freight cars are too big to pass a high platform. Sometimes guantlet
tracks are built to allow freights to pass. Also, high platforms may
make emergency servicing more difficult since the platform blocks
access to the underside of the train.