Neil Williams wrote:
"Adam H. Kerman" wrote:

When berthing at a high-level platform, a trap door is lowered,
covering the steps in the vestibule.

Thanks.

What would you call it?

I don't think we'd have a name as we don't have any - the UK is all
high platformed, or for the rare low ones (not US low) there are
usually wooden steps left on the platform.

I'm always amazed how well these platforms were built that they survived
120 years with minimal maintenance.

The only thing even vaguely like it is the retractable step on
Metrolink trams in Manchester, but I think the platforms are now all
high so they are unused now. All other tram systems in the UK are
all low platform with low floor trams.

The vestibules of cars that run in the Muni Metro subway in San Francisco
(the level above the BART subway in Market Street) when it opened in the
mid 1970's had steps that rise up for floor heigh boarding in subway and
lower for outlying stations with standard-height platforms. It didn't
always work reliably.