Could Cambridge Be Britain's Next Underground City? Tunnel Plans Re-Emerge as Growth Pressures Mount

New reports warn traffic congestion could more than double within five years, prompting renewed examination of underground transport, light rail and rapid transit options.

Cambridge could one day join London, Glasgow, Liverpool and Newcastle as one of only a handful of UK cities with an underground transport network, as planners explore ambitious solutions to accommodate unprecedented levels of future growth.

Fresh analysis commissioned as part of the Government's plans to transform Cambridge into a global science and technology hub suggests existing transport infrastructure will struggle to cope unless major intervention takes place.

With proposals for around 150,000 new homes by 2050 and continued expansion of research, technology and life sciences industries, transport planners are now assessing a range of mass transit options—including the possibility of constructing tunnels beneath the historic city.

Congestion forecast to worsen dramatically

Confidential reports obtained through Freedom of Information requests paint a stark picture of Cambridge's future transport network if significant investment is not delivered.

The documents conclude that under a scenario where only limited transport improvements are introduced, traffic volumes could rise by more than 30 per cent over the coming years, while time spent in congestion is expected to more than double.

Incremental measures such as junction improvements and additional bus priority lanes are described as offering only marginal benefits, leading planners to identify a strong case for introducing a high-capacity Mass Rapid Transit (MRT) system.

The challenge reflects Cambridge's unique geography. Streets originally designed centuries before the arrival of motor vehicles are already under pressure, with future housing and employment growth expected to intensify demand.

Underground option returns to the agenda

Among the options being examined are tunnelled sections beneath the city centre—an idea that has surfaced before but has never progressed beyond the planning stage.

The concept bears similarities to the former Cambridge Autonomous Metro (CAM), proposed several years ago under the previous Combined Authority administration. That project envisaged approximately 50 kilometres of new busways, including around 6.4 kilometres of underground tunnels.

Despite technical support, estimated costs of between £2 billion and £4 billion ultimately led to the project being abandoned.

However, the latest reports suggest tunnelling beneath Cambridge remains technically achievable, citing comparable engineering projects undertaken in similar geological conditions and constrained urban environments.

While engineering feasibility appears positive, the reports acknowledge that underground construction would require substantial upfront investment and careful management of heritage assets, utility infrastructure and construction logistics.

Shorter tunnel proposal gains attention

A more modest alternative has also emerged from independent transport campaign group Cambridge Connect.

Rather than constructing an extensive underground network, the organisation has proposed a 4-kilometre tunnel linking Cambridge railway station with the western science and research campus.

The scheme has been estimated to cost approximately £300 million for the tunnel itself, with underground stations potentially adding around £100 million each.

Supporters argue Cambridge's clay geology makes tunnelling comparatively straightforward by UK standards, although they acknowledge detailed engineering and design work would still be required before any project could move forward.

The proposal is designed to minimise disruption to the city's historic core by avoiding as many heritage buildings and river crossings as possible.

Light rail and bus improvements remain under consideration

An underground railway is only one of several options currently being assessed.

Cambridgeshire and Peterborough Combined Authority is also examining light rail alongside improvements to existing public transport infrastructure.

One study considered converting the region's guided busway into a light rail system but concluded that doing so would require prolonged closure of the existing route while offering little financial advantage over constructing an entirely new tram network.

At the same time, additional busways are already planned between Cambourne and Cambridge and in the south-east of the city, while the recently opened Cambridge South railway station is expected to strengthen regional rail connectivity.

Longer-term proposals also include redesigning several major roads—including Mill Road, Milton Road, Histon Road, Hills Road, Trumpington Road and Newmarket Road—to accommodate dedicated Mass Rapid Transit lanes. Some options would introduce one-way traffic systems or restrict access for general traffic altogether.

No preferred solution yet

Despite renewed interest in underground transport, officials stress that no decisions have been taken.

The Cambridge Growth Company and Cambridgeshire & Peterborough Combined Authority say they are jointly developing the Strategic Outline Business Case for a future Mass Rapid Transit network and continue to evaluate every available technology and route option.

Both organisations have emphasised that the published technical reports are intended to inform the evidence base rather than indicate a preferred solution.

As Cambridge continues to position itself at the centre of the Government's economic growth strategy, one conclusion appears increasingly clear: maintaining the city's global competitiveness will depend not only on building homes and laboratories, but on creating a transport network capable of supporting one of Britain's fastest-growing urban economies.