Paul Corfield wrote:

There are quite severe limitations as to what can be coded on the back
of a ticket and what the gates can recognise...

I'm not sure why this is relevant. Surely as long as the ticket carries
basic information such as:

- start point
- end point
- operator (or 'any')
- route (in the sense of the small number of options actually available
for that journey, e.g. 'not London' or 'any reasonable')
- start date
- end date
- adult/child

the logic to permit or refuse passage can be in the gate (or more
precisely its controller) - I assume recent gate installations have a
reasonably decent Windows PC or equivalent on board, so this can't be
too hard to achieve, can it?

Steve Adams