Underground stations with bare concrete walls, no canopies over entrances, no escalators from street to concourse levels and fewer ticket machines are among the "value engineering" elements of the planned Dublin metro line linking St Stephen's Green with Swords.
According to documents released belatedly under the Freedom of Information Act, the Railway Procurement Agency (RPA) said these "trade-offs" were needed to cut the capital cost of the project to €4.58 billion - an estimate cited in one letter dated July 8th, 2005.
Though all monetary figures in every document were blacked out to maintain strict confidentiality surrounding the metro project, it is possible to discern on close inspection that the overall cost of this 17km line was estimated by the RPA at €4.58 billion in 2004.
The relevant letter from Julie O'Neill, secretary general of the Department of Transport, to David Doyle, deputy secretary general of the Department of Finance, noted that this figure comprised "direct construction cost, risk contingency, fees, insurance and VAT".
In 2003, an RPA estimate that a metro line linking Dublin airport with the city city centre would cost as much as €4.8 billion led to protests from politicians and commentators who believed that the price was too high compared to other European cities, particularly Madrid.
Two years later, Ms O'Neill explained that the more recent figure of €4.58 billion was "the estimated cost that a private bidder would have to spend to build the metro before taking financing costs into consideration", based on the RPA's more economical proposals.
Since then, the estimated cost would have risen due to "construction inflation" as well as the commitment made by Fianna Fáil before last May's general election to route the line underground through Ballymun and the plan to provide an additional station at Parnell Square.
Estimates of how much it will cost to go underground in Ballymun, rather than at surface level along its main street as originally proposed, range from €200 million to €400 million. The cost of the additional station, even with no frills, would be as much again.
In its outline business case for metro, submitted to the Department of Transport in November 2002, the RPA said the benefit-to-cost ratio of a line from Swords to the city centre would range from 0.65:1 to 0.81:1, based on discount rates of 5 per cent and 3.5 per cent respectively.
The equivalent benefit-to-cost ratios of a line from Swords to Bray were put at 0.91:1 or 1.14:1. In other words, the only metro that would pay off in economic terms would be a line running all the way from Swords to Bray (assuming a 3.5 per cent discount rate).
By comparison, as RPA chief executive Frank Allen told the department in February 2005, the benefit-to-cost ratio of a city centre link between the two existing Luas lines would be 3.6:1 or three times more than the best scenario painted for the metro line's performance.
But the agency was undeterred by its own projections. "It is important to recognise that standard cost-benefit analysis [CBA] includes only those benefits that can be easily monetised and as a result ignores some of the most important benefits of improved public transport.
"It is largely for this reason that major international transport projects have been justified with CBA results of less than 1:1," it said. However, the only two examples cited in the report were London's Docklands Light Railway (0.5:1) and Jubilee Line extension in London (1:1).
In both cases, according to the RPA, the investment was justified on the basis of wider benefits of regeneration and social inclusion in London's docklands. Similarly, it argued, Dublin's economy, society and environment would benefit from building a metro serving the airport.
But the report conceded that an airport-city centre line "has a relatively poor economic performance". This was to be expected as it included "the most expensive part of metro . . . without yet reaching the range of markets" that would be served by extending it to Bray.
Although the government had decided in January 2002 to proceed with a metro linking Swords with Bray, the southern leg of this route - now partly served by the Sandyford Luas line - was not included in its Transport 21 investment programme unveiled in November 2005.
Instead, a second orbital metro line linking Tallaght with Ballymun, via Clondalkin and Blanchardstown, made it into the €34.4 billion programme - even though none of the documentation released by the Department of Transport shows that it was subjected to any study.
In its outline business case for the Swords-Bray metro line, the RPA estimated that it would carry 59 million passengers per year, of which nearly nine million would be going to or coming from Dublin airport - representing just 20 per cent of all airport-related journeys.
According to the RPA, metro patronage "is highly dependent on the extent of system phasing and implementation of a sustainable urban development strategy which supports public transport" - notably the adoption of "road demand management" (ie, congestion charging).
As its November 2002 report said, the RPA "has not included road demand management in its central economic case. If the Government implements a road demand management strategy before metro opens, it will substantially improve the metro business case".
Even though the projected 59 million passengers a year would be about three times what the Dart carries, the agency predicted that patronage could rise by up to 20 per cent annually and 30 per cent at peak times if road congestion charging was introduced in Dublin.
With the metro expected to cause land values to rise in the area it serves, the RPA said the best way of capturing at least some of these gains to offset costs would be to use Section 49 of the 2000 Planning Act to levy all new developments within a 1km radius of each station.
In its cost-cutting "revised proposal" for the first phase, submitted in June 2003, it drew attention to the proposed savings, saying they "do give rise to certain trade-offs (ie, lower station specification than in metros in cities such as Copenhagen and elsewhere)".
The RPA also pointed out that the introduction of 24-hour working, if permitted in Dublin, would reduce the tunnelling construction timetable by three months, and it recommended "24-hour tunnelling in areas where its impact will be low" - mainly non-residential areas.
"Economic analysis shows the revised metro proposal to be much stronger in cost-benefit terms", according to the agency. The benefit-to-cost ratio had now risen to 1.31:1, compared to the much lower ratios projected in the outline business case of November 2002.
The RPA also proposed that the Government should simply announce an alignment for the airport-city centre route, without prior public consultation, saying that "a Government announcement of the route would reduce the risk of [legal] challenge" in the High Court.
At the time, it was assumed that the proposed metro line would be approved without further delay by the Cabinet sub-committee on infrastructure, so that it could be built over four years from 2006 to 2009 as a public-private partnership (PPP) project.
"Cost estimates were prepared in anticipation of a Government decision in December 2002 and subsequently, following submission of the revised proposal, a Government decision in mid-2003. Estimates need to be adjusted to take account of escalation in capital costs since then".
As the RPA noted in March 2005: "Twenty months have now passed since submission of the revised proposal, and RPA has stood down its engineering, financial and legal consultants. It is estimated that remobilising this team will take four months.
"Adding this remobilisation to the 20 months equates to a 24-month overall delay from when the revised proposal was submitted. This time needs to be added to the programme envisaged in June 2003, thus giving a revised construction end-date of December 2011".