A conservative approach by the Department of Transport to ordering replacement Dart train carriages will lead to increased reliability issues on the Dublin rail network, likely cost the State more when the trains are ordered, and will delay the expansion of other train services, it has been claimed. Earlier this year, the Department of Transport claimed the delay in ordering the trains -- replacements for the existing 41-year-old Dart carriages, which are suffering daily breakdowns and affecting local and intercity services -- was due to a review of the National Development Plan.