When in the mid-1990s I established that a tram system in Dublin would be incapable of handling the volume of traffic that would eventually be created by reopening the old Harcourt Street rail line, I raised this issue first with the engineering consultants who were designing the system and with the civil servants involved, then with successive ministers for transport.
I pointed out in 1997 that since the project had been initiated at the start of that decade, Dublin's population, employment and car ownership had all been rising almost 2½ times faster than had been projected by the Luas planners. Trams have a limited capacity and a full-scale train service like the Dart was going to be needed.
It is now clear that far from exaggerating the capacity problem in 1997, I significantly underestimated it. The Luas planners had forecast inbound peak traffic in 2001 at 2,100 during the peak morning hour - or 2,800 if feeder bus services to the Luas were provided. In the event, no feeder buses have been provided - presumably because of objections from Dublin Bus and because the Government has failed to provide for a transport co-ordination system in Dublin.
Nevertheless, last year, even without such feeder bus services, the peak-hour inbound flow on weekdays had already attained a figure of 4,000, with an even higher flow in the peak half-hour, a 15 per cent increase above the 2006 level.
It is now clear that apartments and offices nearing completion in the Sandyford area will push this peak traffic volume from Sandyford up to about 5,000 by 2011.
That's barely half the story. A decade ago it was officially estimated that the extension of the line to Cabinteely - now extended to Cherrywood via Stepaside - would increase the traffic volume by two-thirds, ie to 8,500 in the peak hour, which means that 5,000 passengers will be seeking to arrive in the city between 8.30am and 9am.
These trams accommodate 60 seated passengers. Ten years ago the Luas planners said the vehicles would also be able to accommodate 210 standing passengers at a "normal comfort level". However, because of the inadequacy of the system the extreme peak half-hour each tram is now taking a total of 320 passengers - 50 more than that "normal comfort level".
Consideration is now being given to trams 30 per cent longer than the present vehicles, into which it is proposed to squeeze, at great discomfort, 425 passengers - 350 of them standing.
Even with such intolerable overcrowding on journeys of up to 45 minutes, to be able to transport 5,000 passengers in the peak half-hour, these very large trams would need to operate at a 2½-minute frequency - which I understand is the current ambition of the Railway Procurement Agency that runs the Luas.
However, as I pointed out 10 years ago, such a frequency would create unacceptable traffic problems for our city-centre bus services - especially since it is now proposed that new giant trams run along Dawson Street, Nassau Street, the bottom of Grafton Street and College Green. There they would have to share this street space with 61 per cent of all Dublin's buses, making bus travel from many suburbs to the city centre virtually impossible.
Ten years ago I failed to persuade ministers of the need to build a metro on this route rather than a Luas tramway.
In 1997 a new minister, Mary O'Rourke, accepted the undesirability of blocking the streets between St Stephen's Green and O'Connell Street with trams but contented herself with starting the Luas to Sandyford from St Stephen's Green, rejecting the need for a city-centre metro tunnel.
Three years later, however, she accepted that this had been a mistake and announced that it would be necessary to convert the Luas into a metro heavy-rail service, which, she said, would involve providing for tunnel construction through the city centre.
Unhappily, five years after that, in July 2005, a new minister for transport, Séamus Brennan, despite being himself a TD for South Dublin, announced that the city-centre tunnel for the high-capacity metro from Swords and the airport would be halted at St Stephen's Green, where, I have been told, the tunnelling machine will then be left!
The Government could and should decide to extend this tunnel the short distance to Ranelagh, which would enable the grossly inadequate Luas to be become a metro right out to Cherrywood.
The marginal extra cost of thus extending the new tunnel could be substantially offset by a combination of savings from scrapping the replacement of Green Line Luas trams by 52-metre monsters and by abandoning the costly and disruptive proposal to duplicate the O'Connell Street-St Stephen's Green metro with a parallel Luas extension through Dublin's centre-city streets.
There are two questions that the Government must be asked to answer now in connection with this project.
Firstly, has the Minister for Finance's requirement of February 2006 that all significant capital projects must be appraised and implemented in line with his department's capital appraisal guidelines been applied to the proposal to duplicate the metro line between O'Connell Street and St Stephen's Green with a parallel on-street Luas?
If so, does this study show that the marginal extra revenue generated by this parallel Luas operation would justify the cost of constructing and running it, plus the disruption cost of its construction?
Secondly, do the plans for the extension of the Luas line to Cherrywood include provision for its eventual conversion to a metro, or is this extension, like the existing Luas at Beechwood and Stillorgan, to involve more level crossings that for metro purposes would need to be replaced with bridges or tunnels?