Pensioners and disabled people will be able to travel free by bus the length and breadth of Scotland from Saturday.
The card scheme gives free travel across Scotland
The national scheme launched by First Minister Jack McConnell in Glasgow on Friday has come into effect.
The Scottish Executive has allocated £159m for the first year, so that anyone over the age of 60 and people with reduced mobility can travel free.
The scheme operates through a national entitlement card, which has been applied for by 750,000 people.
Journeys from Scotland to Carlisle and Berwick will fall within the scheme.
Talks are still under way with the industry on how it will work with longer single-stop cross-border services such as Glasgow to London.
Mr McConnell said: "This is a great day for older and disabled people in Scotland. It will make a massive difference to their lives."
The executive estimates that 1.1 million people are eligible.
As well as free bus travel, the scheme extends to older and disabled islanders who will be entitled to two free return ferry trips to the mainland.
Winnie Campbell, 90, from Kilmarnock said: "This is going to be a real bonus - the biggest thing of all is that I'll be able to travel before nine o'clock. It's going to save me quite a bit - half my pension goes on bus fares."
Gordon Brown gave his backing to the scheme
Bus companies do not know how many extra passengers to expect, but businesses have been gearing up for the introduction of the card.
There are concerns that some of the most isolated pensioners and disabled people will not benefit from the scheme.
The Scottish Executive said it expected cards would get to 97% of applicants in time for the scheme's launch, but there have been some complaints about not receiving cards, despite making early applications.
Retired teacher Leslie Horne, 65, from Edinburgh said he was told his card had been processed nearly two weeks ago but he still has not got it.
He said: "I'm not pleased and I have a good friend who is also upset, he applied almost immediately and he still has not got anything.
"I was looking forward to the inaugural trip, my expectations had been built up and then dashed down."
Mr Horne said he still had his existing local card, but that it only covered the Lothians and did not let him book journeys further afield online.