Traffic is likely to be the crunch issue in An Bord Pleanala's forthcoming decision on whether the Liffey Valley shopping centre at Quarryvale, strategically located at the junction of the M50 and the N4, should be doubled in size.
Barkhill Ltd, a consortium controlled by the Cork-based developer, Mr Owen O'Callaghan, and the Duke of Westminster, is seeking planning permission to add nearly 250,000 square feet of retail space, including a Tesco supermarket.
A decision by South Dublin County Council, which is already in receipt of substantial rates from Quarryvale, to grant permission for the proposed development is being contested by RGDATA, representing the independent grocery sector.
The appeals board, in a move which has been strenuously opposed by the developers, requested the Dublin Transportation Office (DTO) to submit its observations after it became clear that the county council had made its decision without the benefit of such advice.
In a letter to the board, the DTO's director, Mr John Henry, said there was already traffic congestion at the N4/M50 interchange and the proposed development "will exacerbate this and undermine the strategic function of these routes".
He said the volume of parking proposed, at just over 6,000 spaces, was "well in excess of the parking standard" and should be "significantly reduced" to 4,630 or less, adding that consideration should be given to charging for parking on the site.
Mr Henry maintained that such charges would serve a dual function of deterring traffic and raising revenue to improve bus services from Lucan and Clondalkin - the stated catchment areas - which did not have easy access to Quarryvale.
According to the DTO, the scale of the Liffey Valley shopping centre, if the proposed extension was permitted, would make it a "regional attraction" and, because of its pivotal location on the M50, it would be "highly accessible by car from a large catchment area".
Mr Henry noted that one of the central elements of the Dublin Transportation Initiative strategy, adopted in 1994, was to reduce reliance on car use by controlling speculative commercial, retail and leisure development along the M50 corridor.
He also drew An Bord Pleanala's attention to Government policy as set out in Sustainable Development - A Strategy for Ireland (1997), which stresses the need to reduce the growth in travel demand and to place increasing emphasis on public transport.
Similarly, the Strategic Planning Guidelines for the Greater Dublin Area, published last April, had also stressed the need to ensure that development throughout the region "will be increasingly related to a significantly enhanced public transport system".
Mr Henry also noted that South Dublin County Council's 1998 county development plan had pledged "to promote, facilitate and co-operate with other agencies in securing the implementation of the transportation strategy for the Dublin region".
In the light of these policies, and the presumption against locating large shopping centres close to national roads, he said Quarryvale "clearly . . . cannot be considered to satisfy the criteria" for major retail schemes and should be used for warehousing or manufacturing.
Reid Associates, planning consultants for the development, argued that neither the planning Acts nor the 1994 planning regulations empowered An Bord Pleanala to invite the DTO to make a submission and requested the board to dismiss it without further consideration.
In 1992, when the 180-acre Quarryvale site was rezoned as a "district/town centre", a ceiling of 250,000 square feet was imposed on its net retail content. However, this cap was lifted by South Dublin County Council in its current county plan, adopted in 1998.
A report by the former county planning officer, Mr Enda Conway, recommending that the proposal to double its size should be approved, said the "fundamental consideration" was whether this would be acceptable in the context of the relevant planning policies.
In his report, he argued that a major supermarket was "badly needed in view of the existing deficiency of food stores provided in the complex", though he accepted that "the methodologies employed in retail assessment do not amount to an exact science".
Dealing with the traffic impact of Barkhill's scheme, he noted that the N4 had already been widened to six lanes, with a new interchange at Fonthill Road to serve Quarryvale. Further improvements would be needed whether or not the extension proceeded.
According to him, the traffic generation and parking provisions were "acceptable" provided the developers contributed £400,000 towards a bus priority scheme on Fonthill Road and £60,000 towards the provision of cameras to monitor traffic.
The developers are also prepared to allocate a 400-space "park-and-ride" site adjacent to the main car park at Quarryvale, a proposal welcomed by the DTO which stressed in its submission that this was proceeding independently of the current application.