The Government, having been blamed for spending money badly, has to convince a sceptical public that things have changed, writes Mark Hennessy, Political Correspondent.
Never in the history of public transport has so much been promised by so many Ministers, backed up by so little paperwork.
The 10-year transport plan contains enormous figures: €34 billion, €8 billion of which will be private developers' money, over 1,000 kilometres of road.
Usually major Government policy launches - and this Government has produced many of them - are accompanied by weighty documents, hundreds of pages long. The provision of such tomes, of course, does not mean the policy is any more likely to be realised. The health strategy is proof of that.
The lack of paperwork for the transport plan does not mean it is less likely to be achieved, although it is surprising for an initiative 11 months in the making.
However, the Government first faces the task of convincing a doubtful public that change will happen, and on time, and on budget.
Based on overspends on Luas, the rail tunnel and other projects, the Government has earned a reputation for being profligate with State money.
The initial radio and television headlines last night were manna from heaven for an embattled administration: "Major investment", "radical", "historic".
The political strategy is obvious. First, the Government knows it must stop being an object of ridicule, and must propose a new vision.
In time the third leg of the strategy - already seen being warmed up at the Fianna Fáil Ardfheis in Killarney - will come into action: to scare the living daylights out of voters tempted to vote for Fine Gael, Labour and the Greens.
The devil of the Government's transport plan will be in the detail and the Ministers gathered in Dublin Castle yesterday were sticking to the broad brush.
Yesterday Minister for Finance Brian Cowen and Minister for Transport Martin Cullen insisted that every major roads project completed since 2001 had come in on time and on budget.
Mr Cowen promised ruthless control to get value for money and said 18 of 20 projects under way were equally well behaved.
Such is the case, in as much as it can be judged, with the Monasterevin bypass, and the expected early openings of the Fermoy and Kilcock/Kinnegad motorways.
However, the public is sceptical.
Last night, the argument raged between the Government and the Opposition over how much of the €34 billion is new money.
"This is the most environmentally friendly transport package in the country's transport system, because it never goes anywhere," said Fine Gael.
A significant part of the policy, dubbed Transport 21, is comprised of repackaged proposals, promised before but not delivered. Motorways will be in place between Dublin and all of the major cities by 2010, which the National Development Plan promised for 2006.
The Luas lines will be joined up by a Government that decided less than seven years ago that such a thing was impossible for all sorts of reasons.
Cowen acknowledged that €10 billion of the money mentioned yesterday was already pencilled in.
Commuter services between Midleton and Cork were included in Cork County Council's last development plan. Indeed, it is the third time they have been announced. Séamus Brennan did so shortly before he had to make way, reluctantly, for Martin Cullen.
Nevertheless, the 21st century model of public transport would revolutionise life in the capital, and surrounding regions if put into effect.
Yesterday Brian Cowen was emphatic. It had to be done, otherwise long-term economic growth would be affected.
If one strips away the already-promised roads and railway improvements, Transport 21 is clearly targeted at Dublin and the key contiguous constituencies.
The Government's version of the western rail corridor is a far cry from the one put forward by vocal lobby groups across the Shannon.
Instead of running services between Sligo, Galway and Limerick and on to Cork within five years, the Cabinet has opted for a less ambitious proposal.
Ideas could only be accepted if they made sense, Martin Cullen said, and, though he did not say it, much of the campaigners' arguments were questionable.
However, logic may prove to be little comfort in rural Connacht constituencies next time out, particularly for increasingly nervous Fianna Fáil TDs.
Careful, perhaps, not to make promises that will come back to haunt him, Cullen has not committed to delivering new projects before the expected date of the general election in early 2007.
Though the new plan may not mean much to voters next time, Fianna Fáil and the Progressive Democrats hope that the public will begin to accept that change is coming.
During his time in Transport, Séamus Brennan realised that the public only pays attention when it is presented with huge change arriving in one step, a la the M1 motorway that has revolutionised the lives of those driving to Belfast from Dublin.
His successor, Martin Cullen, has had a dreadful time in Cabinet, following his mishandling of electronic voting and the row over PR adviser Monica Leech.
Transport 21, even if it is really run by Brian Cowen from the Department of Finance, gives Cullen a new opportunity to salvage his reputation.
However, he is on a short leash. During the presentation yesterday, it was clear that Brian Cowen would call the final shots.
And Cowen did not seem unhappy that everyone knew it.