Comment & Analysis: MetroLink is approaching the stage where transport agencies issue a call for companies to bid to construct and operate the line, so its worth spending time debunking the many myths, misinformation, and misdirection surrounding the project. Its best to address issues in separate articles, and the first of these today examines passenger capacity.For those not following the MetroLink saga to date: The route is a proposed near-19km high-capacity, high-frequency railway with 16 stations between Estuary, north of Swords town, to Charlemont, at the northern tip of Ranelagh south of the city centre. The project has full planning permission. Passenger-carrying capacity isnt generally a myth or source of misinformation in itself. But the level of capacity is widely misunderstood, to the point that it fuels many misconceptions about the project. Some of which will be covered separately in other articles, but capacity is such a key point, lets focus on that here.Capacity is the strongest reason to invest in railway lines, and especially urban rail. The achievable level depends on several design and operational factors, including platform length, degree of segregation, train width, train lengths, train frequency, and the speed of acceleration and deceleration.MetroLink is 100% grade-separated from all traffic, which means there are no level crossings. Its also automated (driveless), which means more trains can run because of factors such as consistentmovement, and it features passenger-screen doors that increase safety and reduce delays.While MetroNorth platforms will be about 10 metres longer than the longest Luas trams, each train will also gain space by being wider than the trams. These features combined allow MetroLink to carry up to 20,000 passengers per hour in each direction.Thats compared to 6,400 vehicles per hour per direction on the M50, with a low occupancy rate. An estimated 87% of vehicles during the morning peak rush hour are single-occupancy, so even if most of the remainder are carrying 3-4 people, the capacity on the M50 is still much lower.IMAGES: Edmonton Transit Service.So, when anyone says MetroLink could be replaced by Luas, a spur of the Dart line to the airport/Swords, or even buses, do not believe them. For capacity reasons alone, it is just not true.