In message . com, Joe
writes

Whilst waiting for someone at Mortlake today, and saw the level
crossing going up & down every 5 mins (I dread to think what it's like
during the peak),

The opening and closing routine tends to be better on weekdays,
especially during the peaks, than at weekends. Nevertheless, it is a
very busy line

I was wondering, what is the busiest crossing (in terms of Number of
trains) in the London area,

Last time this was asked here (only a few months ago) it was generally
reckoned that the busiest is the one you saw (along with its three
adjacent siblings). Do a Google Groups search in uk.transport.london for
the thread "London's busiest level crossing?"

and what crossing is closest to Central London?

Google again for the thread "London's closest pair of level crossings?"

--
Paul Terry