Sir, – Senator Lorraine Clifford-Lee, in her letter (July 13th), takes Senator Michael McDowell to task in relation to his column on the cost of the proposed MetroLink.She is quite correct in stating that MetroLink is “not an airport shuttle”. She rejects the alternative of an airport rail spur from the northern commuter line on the basis that this line is overcrowded and faces “congestion through Connolly Station”.However, she may not be aware that the original Dublin Area Rapid Transit (Dart) proposal published by CIÉ in 1975 would, if it had been delivered, have greatly increased the capacity of all of the existing commuter lines and removed the existing Connolly/Tara Street/Pearse congestion – by routing the northern line through the city centre using the proposed Dart underground tunnel and on to the Sallins commuter line.This would allow the Maynooth/Dunboyne line to run uninterrupted to Bray and Greystones.The integrated 1975 Dart plan also made provision for a connection to the then proposed new town of Tallaght as well as an option to connect to the airport and Ballymun, thus also serving all the housing lands along the north fringe from Belcamp to Baldoyle.Clifford-Lee also omitted to mention that the earlier Metro North proposal, as well as the Dart underground with a shared station at Stephen’s Green, were brought through the Railway Order process at a cost of well more than €200 million and approved by An Bord Pleanála in 2010 and 2011 respectively, only for the then minister for transport Leo Varadkar to abandon both projects due to a focus on the short-term impact of the economic crash.With a booming economy and rapidly rising population, building the current MetroLink project (whatever the cost) may be of benefit to a small proportion of commuters. However, the absence of the vital Dart underground means that the multibillion-euro plans to deliver “Dart+” to the Maynooth, Dunboyne and Sallins areas and the planned extension of the Dart to Drogheda will result only in further congestion at Connolly Station. This will result in an ongoing fractured and overloaded public transport system for future generations.The lack of progress in the 50 years since the far-sighted 1975 Dart proposals represents the single most significant failure of leadership in the development of the Greater Dublin Area. It makes no sense to spend more money on the so-called Dart+ proposals in the absence of the vital Dart underground section.In the end, the cost of infrastructure is not always the issue, rather the continuing cost to the entire country and its citizens of the failure to deliver the integrated and coherent mass transit system that Dublin deserves. – Yours, etc,Adrian P Conway,Chartered engineer,Kilcloon,Co Meath