Flat numbers on a card indicates that it is for online use only. I'm surprised that Cross Country accept it onboard - do they swipe it or use Chip+PIN?
Strange one Northern don't except my Visa card it hasn't got embossed numbers (raised) but Crosscountry do, both on train why is this?
I am begging to suspect this 'not embossed' => 'online only' is no longer true. Rather like 'all swans are white', until the black swans were found.
See 1.1.4 here http://www.barclaycard.co.uk/business/documents/pdfs/procedure_guide.pdf
That describes a card which is "acceptable for electronic and paper fallback transactions". It also says the account number may be embossed and goes on to mention that if the card number is not embossed, the expiry date will not be embossed.
11. All unembossed Visa Electron and Maestro (issued
outside the UK) transactions must be processed
electronically and must be authorised. In the event of
terminal failure, or if the card reader does not read the
required details, return the card to the customer and ask
for an alternative method of payment.
12. Remember that an Electron card number must never
be key-entered for a sale transaction.
My understanding is that:
An unembossed card issued in the UK will require all transactions to be authorised individually online.
An embossed card ought to have some degree of offline capability encoded, however these can also be online only cards.
Historically the reason for unembossed cards was to prevent use in the old fashioned paper imprint machines - which were offline transactions. My understanding is that now, if a merchant is having to use their imprinter as a fall back they are required to call for authorisations for everything above a very low floor limit, making this feature no longer relevant.
I also take this as implying that the only unembossed cards should be Electron/Maestro type.
From a quick scan of that Barclaycard document, I don't think they are required to call for authorisation, but they are advised to as they would otherwise be left short if the card issuer were to decline the transaction when it was presented afterwards.