Digging tunnels for Bristol’s planned underground rail network would be “relatively easy”, according to a tunneling expert.

Martin Knights says that building a mass transport system would not pose “more challenges than any recent tunneling that has been carried out in London”, including the recently completed Elizabeth Line.

Knights has been leading and managing all aspects of civil engineering and infrastructure for more than 45 years, with a special technical emphasis on tunneling and underground urban engineering projects.

In an interview with new civil engineerKnights said that “it would be relatively easy to use tunnel boring machines (TBMs) as they could support the ground quite well.”

He added: “What has been done with Crossrail can definitely be achieved in other big UK cities.”

Knights said detailed ground investigation could overcome the challenge of unknown coal measurements, while Bristol could look to the Dublin Metrolink as a model for crossing rivers and tunneling to the same depth.

However, the funding of the multi-billion dollar Bristol project could be what prevents underground trains from running beneath our city for the foreseeable future.

“The political will of the mayor will be an important ingredient to get the project off the ground,” Knights said, apparently referring to the West of England mayor, Dan Norris, who officially says Bristol will not have a subway.

“They will ask if they can afford it and weigh that against the risks of not doing it. It is feasible from an engineering point of view, but the problem is getting the financing.

“I saw initial figures estimating £4bn and that seems to be in the right order, but often with these projects the costs can keep rising…

“Engineering is solvable. There will be challenges, but everything is technically feasible.”

Lead photo: Martin Booth

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