Brian Caulfield, associate professor with the School of Engineering at TCD, joins us this week to examine MetroLink, formerly known as Metro North. After years of delays the project appears to be back on track - but will it actually come to fruition this time? How much will it cost and how important it is in terms of the city's development?The Explainer is brought to you by The Journal. Providing open access to valuable journalism in Ireland has been the aim of The Journal for a decade. You can contribute to ensure we can keep questioning, investigating, debunking, explaining and informing at www.thejournal.ie/contribute/