SUCH as its designers may seek to deny it, the port tunnel is almost bound to be the first phase of a full Eastern Bypass motorway linking Whitehall with Stillorgan, via Dublin Port and Sandymount Strand. Indeed, it follows almost exactly the same route as the northern segment of the bypass proposed in 1993.
The same consultant engineers, Ove Arup and Partners, and the Austrian firm of Geoconsult, who together drew up an environmental impact and feasibility study for this largely tunnelled Eastern Bypass, have designed the current scheme. They also compiled the three volume environmental impact statement on it.
Although the Eastern Bypass was officially ruled out in 1993 by the then Fianna Fail Labour coalition, the same government decided a year later to double the size of the proposed port tunnel from a single bore, two lane route to a twin bore, four lane dual carriageway, contrary to the recommendation of the Dublin Transportation Initiative.
The government's argument was that this would yield two tunnels for not much more than the price of one, a mere £20 million or so extra. This line was strongly favoured at the time by the then Minister for Finance, Mr Bertie Ahern, because it would bring some relief from heavy traffic to his constituents in Drumcondra.
As designed, the proposed port tunnel would be an extension of the M1 motorway, taking it as far as Dublin Port. The motorway would feed directly into the tunnel portals at Whitehall. Motorists bound for the city centre would have to turn off onto a slip road if they wished to use the present route via Drumcondra.
Critics such as Prof Simon Perry of Trinity College fear that the likely congestion this would cause in the north port area, and in Sandymount, makes the completion of a full Eastern Bypass almost inevitable. It would certainly require a new bridge over the River Liffey, costing an estimated £8 million, to provide some relief in the short term.
For at least 25 years, the Eastern Bypass has been on the agenda in one form or another and there is still an engineering imperative to complete the "motorway box" around the city, rather than settling for the M50 "C-Ring" with a spur leading into the port. The only problem is that we may have to pay for the rest of it, with no EU funding.
Mr Gerry Murphy, Dublin Corporation's project engineer, denied that the design team was involved in "machinations to do anything that leads on to the next stage"; this would be a matter for the Government to decide in 10 years time.
However, it is clear that a north south alignment was chosen for the port access route, rather than an east west one, at least in part to keep the Eastern Bypass option open. "It's true that that's how it came about, that's its genesis, and there's no doubt it carries that baggage," Mr Murphy said. "But it still operates superbly well in its own terms.
By comparison, the eastwest Liffey tunnel proposed by National Toll Roads plc "performed very poorly", according to him. Starting just west of Heuston Station and ending in Guild Street, its main drawbacks were that it would not have connected the port with the C ring and would only have catered for half the number of heavy goods vehicles.
Mr Murphy pointed out that only a third of all port traffic was coming from or going to the west or south west of the city, generally via the Liffey quays. Another third had its origin or destination to the north of the city, with 11 per cent as the comparable figure for the south. The remaining 22 per cent begins or ends within the canal ring.
As a result of this and other factors, the real economic benefits of the port tunnel were "enormously greater" than NTR's alternative. This was what the DTI's final report had said, in dismissing both the east west option and a proposed "dedicated truckway" on the route of one of the railway lines serving the port.
The DTI also said there should be no increase in the capacity of radial routes within the C ring, in order to discourage even more car commuting. Yet the economic benefits of the proposed port tunnel, which would serve as another radial route, are based on catering not just for port related heavy goods vehicles (HGVs), but for cars, too.
According to projections, HGVs would account for only 13 per cent of all the vehicles using the tunnel. From the day it opens in the year 2002, the engineers estimate that it will be catering for 32,000 ears and 7,000 HGVs a day. This imbalance is less pronounced if it is measured in passenger car units (pcus) where each HGV is equal to three pcus.
Given these traffic volumes, the engineers argue that the project cannot be cut back to a single bore tunnel to save money. A twin bore tunnel, they say, would also provide "slow lanes" for trucks. In the event of an emergency traffic would continue to flow instead of being backed up for miles.
The design team is acutely conscious of claims that the project cannot be delivered for the quoted cost of £130 million. This figure is already substantially higher than the original price tag of £104 million and there seems to be little doubt that it will rise further.
If changes have to be made to meet the concerns of residents in Marino and Whitehall, additional costs will be involved. The National Roads Authority has indicated that it would be prepared to consider such changes, bearing in mind the cost implications. But the NRA's chief executive, Mr Michael Tobin, has said there is "no open cheque book".
One of the main concerns voiced by Prof Perry, among others, is that the cost of the port tunnel could spiral out of control, perhaps even reaching £200 million, and that this would eat into the funds available to implement other projects which are an integral part of the DTI strategy, such as the proposed Luas light rail system.
Construction of the port tunnel was meant to start this year and be completed by 2001, but it has already been delayed for two years.
