Demand for “millennial railcards” have caused a website to crash as travellers try to buy one of the 10,000 on offer.
The railcard for 26 to 30-year-olds costs £30 for a year and offers a third off most fares in England, Wales and Scotland.
However, the number of cards available is only enough for one in 500 of the eligible population, and are limited to a minimum £12 fare during peak times.
National Railcards apologised for the website issue and was trying to fix it.
The card was announced in Chancellor Philip Hammond’s Budget in November, with him saying it would give “4.5 million more young people a third off their rail fares”.
But only 10,000 went on sale this morning, following a trial in East Anglia.
The Rail Delivery Group said they would be available on a first-come, first-served basis.
But when customers went to the National Railcard website to purchase one, they were asked to “please bear with us” and met with an error message, saying the service was unavailable.
A spokesman for railcard.co.uk said: “We’ve had an unprecedented number of people visiting our site for the 26-30 Railcard.
“Please bear with us, we’ve got the whole team working on it and hope we can have it back up shortly.”
Source: BBC News