Christian Hansen wrote:
On Wed, 19 Jul 2006 02:45:21 +0100, "John Rowland"
wrote:

Unless the seats were centrally locked up by the driver, or better
still, on a time switch.

I have this mental picture of a sadistic train driver flipping a
switch at 4:59 pm and watching 40 people's shocked expressions as
they jump up to avoid being swatted in the bum by their tip-up seats.

The obvious solution would be electro-magnets, energised by a switch. Once
someone gets up and the seat returns to the upright position it stays there
until disengaged. There might be a few people holding seats down whilst
someone else takes over the seat but it wouldn't last for long (especially
at terminii!).