"John Rowland" wrote in message
...

They also allow Oyster cards to be topped up, doubling, at least, the
amount of machines that do. To allow for the machinery to accept
credit / debit cards and deal with Oyster there is insufficent space
to allow them to give change too.

Surely not giving change means that the machine will be fed a lot more
coins and it will have no choice but to hold onto them. This will cause it
to fill up more quickly, or require it to have more space devoted to coin
holding.

Most coins are £1 coins, of which, most would go into the coin vault anyway.
The chutes to hold coins for change and the mechanism for floating machines
take up quite a bit of room. The coin vault is located in the lower half of
the machine.