If you are aged 30 at the time that the Railcard is purchased, you may still travel at the discounted fare throughout the validity period of the Railcard, even if you become 31 years old during that time.
Thousands of frustrated young adults spent hours trying to get their hands on the new 26-30 railcard, dubbed the millennial railcard, when it launched on Tuesday.
Tom Drury, from London, wrote: "The launch of the new railcard is a shambles".
Anthony Smith, chief executive of watchdog Transport Focus, said: "The nationwide trial of the 26-30 railcard is welcome news for hard-pressed passengers and will help take some of the sting out of rising rail fares".
The trial of the 26-30 railcard is part of the rail industry's long-term plan to change, improve and boost communities by enabling more people to travel by train. "Sort out your website to make it fair!' Others said it's worse than 'waiting in the Ticketmaster queue".
Those who missed out can sign up online to receive notification if more cards are made available.
Competition is fierce; an estimated five million British people are eligible for the 26-30 Railcard, which means there is only one for every 500 people in the 26-30 cohort.
A spokesman for Railcard.co.uk said: "We've had an unprecedented number of people visiting our site for the 26-30 Railcard".
The card is aimed at leisure travellers rather than commuters, as it offers no discounts on season tickets and a £12 minimum fare on all journeys between 4.30am and 10am, excluding weekends and public holidays. However, the website was still down as of 2pm on 13th March.
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Despite these restrictions, if you do regularly travel off peak or over long distances, the new railcard could save you a packet.
"Usually, the cost of the Railcard will have paid for itself after one or two trips".
It can only be bought online and must be downloaded to a smartphone.
The release of the second batch of trial railcards comes as Chancellor Philip Hammond - who announced the railcards a year ago - delivers his Spring Statement in the House of Commons today.
This is slightly more nuanced than it first appears. To apply you need a digital passport-style photo, saved on your computer, and a passport, driving licence number or a valid national identity card from the European Economic Area.
How many are 26-30 railcards are on sale?
The main drawback is that there are only 10,000 railcards available, so you'll need to be quick to snap one up.
Rail Delivery Group, the company that is releasing the millennial railcards, has yet to specify when they will be fully rolled out across the UK.