Dave Arquati writes:
The only way I can think of making it more intuitive is to use
"citybound", or perhaps to highlight Zone 1 stations on the line
diagrams. Then again, using citybound would probably add new confusion,
and it would only work for non-central stations.

On the MBTA subway system in Boston, known as the T for short, they
do in fact use "inbound" and "outbound" as directions on most of the
system. In the city center they switch to some sort of destination-
based signage. But their city center is a lot smaller than Central
London, so a large proportion of the stations are outside it.
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