"Jason G Doig" wrote in message
...
What happens however when there is a gap between dates covered by the
tickets, such that the new ticket is actually being purchased after the
previous one runs out? How can I pass through a ticket gate to renew the
card, if I have no valid tickets on the card?

Just pass through on the day that the new ticket starts - it should load the
new ticket and let you through at the same time.

Self-service machines at the nominated station _might_ be able to load
tickets too, somebody will need to confirm that.

--
TC