Picture credit: Leonhard Niederwimmer on Unsplash

An underground metro can help transform a city for both tourists and locals, and it looks like Dublin might finally be getting such a system following more than twenty years of discussions.

After first being suggested back in 2001, as part of the “Platform for Change” report by the Dublin Transportation Office (which is now part of the National Transport Authority), it looks likely this project will go ahead. A team has been appointed for the design, procurement and construction phases, which is expected to cost around €9.5 billion (£8.2 billion).

The high-capacity MetroLink – the first of its kind in Ireland – will cover approximately 19km (12 miles) from Swords in the north to Charlemont in the south. The proposed route runs through central Dublin, with the Tara station less than one kilometre from the famous Temple Bar pub and surrounding watering holes.

Running mainly underground, the final design of the metro involves creating a single bore, twin track tunnel.

Boring the tunnel will happen in two phases, using only one tunnel boring machine (TBM). The TBM will begin south of Dublin Airport and tunnel north, under the airport. It will then be extracted and relaunched at Northwood, ready to tunnel south to Charlemont.

This approach – using the single bore twin track tunnel – is increasingly used worldwide, especially when a route uses automated trains, as the Dublin one will. There are several advantages to this construction method, compared with the other suggested approach, which involved a twin bore tunnel:

 1.  Cost savings

The twin bore method would have required four TBMs, so using a single bore method significantly reduces costs. With twin tunnels, cross passages between the two tunnels must be in place before any work starts on the tracks – so workers can easily be evacuated in an emergency. This is no longer a consideration in the single-bore tunnel, making construction simpler, faster and more budget-friendly.

 2.  Safety considerations

In the unlikely event of an incident occurring between stations, with automatic train operation (ATO) in a single tunnel, evacuation becomes easier. With no driver in place, passengers can evacuate from either end of the train and easily move away from the train. This environment is also more accessible to emergency services. In a twin bore tunnel passengers would need to exit trains via side doors onto narrow walkways, causing congestion both for evacuating passengers and the emergency services trying to reach them.

 3.  Logistical challenges

With the twin bore proposal, the tunnel construction would have resulted in a sizeable construction site both at the Home Farm FC ground, and at the CLG Na Fianna ground. As well as disrupting the grounds for up to seven years, there would also have been significant HGV traffic carrying extracted material from the tunnels at Griffith Park. The Northwood launch site for the single bore twin-track tunnel is less central and closer to the M50, meaning the HGV activity will be outside the city and therefore less disruptive.

The driverless trains planned for Dublin are modelled on the Copenhagen Metro and the Barcelona Metro, where trains are supervised from a control centre. Carriages, stations and platforms are monitored via CCTV. The operational, safety and security staff in the control centre can communicate with passengers through the public address system and passengers can contact the control centre from each carriage.

This ATO includes advanced signalling technology and improves safety during normal operation as well as during disruption and emergencies, as the capacity for human error is eliminated. Platform screen doors – similar to those on parts of the Jubilee line in central London – prevent anyone falling onto the tracks.

The new metro has the capacity to carry up to 20,000 passengers per hour in each direction. It will connect existing air, rail and bus services across Greater Dublin, proving useful for both local people and those flying into Dublin. A journey from the airport to the city centre will take 20 minutes.

It’s anticipated that construction could begin in late 2025, with trains operational by the mid-2030s. It’s a significant project for the city, and an opportunity to create efficient, low-carbon public transport, as well as creating 8,000 construction jobs.

For a project that’s already been discussed for two decades, it’s certainly not a given that it will go ahead, but it’s looking likely it will. Watch this space.

And if you need assistance with the structural elements of an upcoming project, please do get in touch.