The Lower Thames Crossing (LTC) is a major new road and tunnel project that will create a new road link beneath the River Thames, connecting Kent in the south with Essex and Thurrock in the north. The full route will span about 23 km (≈ 14–14.5 miles).

Roughly 4.2–4.25 km of the route will be in twin-bore tunnels — one for northbound traffic and one for southbound. This will make the LTC tunnels the longest road tunnels in the UK.

On the surface, the crossing will link the A2/M2 in Kent with the A13 and the M25 (junction 29) in Essex/Thurrock — offering a direct route between these major roads.

The main goal of the project is to greatly increase road capacity east of London, easing congestion at the Dartford Crossing — for decades the only road crossing of the Thames east of London.

The new link is expected to make journeys faster and more reliable, benefiting both everyday motorists and freight moving between the South-East, the Midlands, and northern England.

What’s new: 2025 milestone and the tunnelling plan

On 25 March 2025, the project received formal planning consent — a major milestone after years of planning, consultation and re-submissions.

According to the agency behind the project, the road is now expected to be built in the early 2030s.

Now — and this is the most recent and significant update — the governing body behind the project, National Highways, has launched procurement of a tunnelling machine for the LTC. This machine will be among the largest in the world.

Key recent developments:

The machine is described as 16.4 metres in diameter — making the tunnel one of the widest in the world.

The same machine will be used to excavate both the northbound and southbound tunnels — a cost- and time-saving strategy.

Procurement (i.e. buying the machine) is expected to complete next year, with tunnelling scheduled to start in 2028.

Work on the northern tunnel entrance — the “launch chamber” from which the machine starts — is expected to begin next summer (2026). The chamber will be 26 metres deep and house a temporary factory to produce concrete segments to line the tunnel.

According to Matt Palmer, Executive Director of the Lower Thames Crossing project, the scheme remains “on track” for completion in the early 2030s.

And Simon Lightwood, Roads and Buses Minister, said that launching the procurement for this “one of Europe’s largest tunnelling machines” is a major step forward for what is a “transformational project.”

Engineering challenges — and how LTC plans to overcome them

The geology underneath the Thames estuary at the LTC site is complex and challenging. North of the river, the ground includes layers of alluvium (clays, silts, peat), soft floodplain soils, and historical landfill — all over chalk substrate.

Because of these conditions:

The project team will need extensive ground treatment before tunnelling begins — including soil mixing to strengthen the soft ground so it can support the huge 16.4 m-wide tunnel rings.

The launch chamber / portal structure for the tunnelling machine will be extremely robust: deep diaphragm walls, piled foundations, and a carefully engineered base slab to resist buoyancy — since groundwater and river pressure will be significant.

Despite these difficulties, the project aims to use cutting-edge tunnelling technology, drawing on experience from large-scale tunnelling through chalk and flint in other UK infrastructure works.

Using a single TBM (tunnel boring machine) for both tunnel bores is part of a “low-carbon, cost-efficient” plan championed by National Highways.

What LTC promises — Beyond just a new road

Supporters of the Lower Thames Crossing emphasise that the project is not just about traffic: it also carries economic, environmental, and community ambitions.

Some of the key promised benefits:

Doubling road capacity across the Thames east of London — meaning far less congestion around the Dartford Crossing, and smoother freight and commuter traffic.

Faster, more reliable journeys, and potentially reduced journey times. Speed limits are expected to be up to 70 mph through the tunnels.

Boost for freight transport and the economy: improving connections between ports in the south-east and the Midlands/North.

Environmental and community enhancements: the project aims to be the UK’s “greenest road.” Plans include creating new public parks, community woodland, perhaps a wetland near the Thames, and new walking/cycling/horse-riding routes. Excavated material will be reused, and much of the road will be hidden underground or behind landscaped embankments/ cuttings.

In short: proponents argue that LTC is an investment in 21st-century infrastructure — balancing transport needs, environmental ambition, and long-term economic growth.

What to watch — Risks, controversies and what might still change

No major infrastructure project of this scale comes without challenges. Some of the outstanding issues and concerns around the LTC include:

Geotechnical risk: The soft, mixed ground on the north side of the Thames means tunnel construction will require careful ground treatment, and the size of the TBM (16.4 m) makes this more complex than usual. Mistakes or unexpected ground conditions could cause delays or increased costs.

Cost and financing: The project is expected to cost up to £10–11 billion.

The government is reportedly exploring private-investment funding models (such as a “regulated asset base (RAB)” approach), but as of now financing still has some uncertainty.

Environmental & community concerns: While the project promises new green space and mitigation, some environmental groups fear the tunnel may still encourage higher car use, lead to pollution near portals, or disturb local ecosystems. In past coverage of the project, such objections have been voiced.

Long timeline: With tunnelling only expected to begin in 2028, and the road potentially opening in the early 2030s, it will be several years before the benefits are felt. Delays — due to funding, engineering, or regulatory obstacles — remain possible.

Why the tunnelling machine procurement is a big deal

The recent launch of procurement for a massive 16.4-metre diameter tunnelling machine represents the shift of LTC from planning to execution. Supporters and project leaders see this as the moment when decades of discussion become real — when the actual digging begins.

Using a single “mega-TBM” for both tunnel bores — rather than two separate machines — is a cost-efficiency and carbon-saving measure. It reduces the environmental footprint of the project by limiting the amount of heavy machinery and energy required.

Moreover, the TBM’s size — one of the largest in Europe — underlines the ambition of the project. Once operational, the LTC will not only ease traffic and boost transport capacity, but also stand as one of the most significant feats of modern British civil engineering.

As Minister Simon Lightwood put it, launching procurement is “a major step forward for this transformational project.”

Outlook — What happens next

Over the coming months — 2026: preparation work begins on the northern tunnel portal / launch chamber, including building the vast 26-metre deep shaft and temporary concrete-segment factory.

By 2027–2028: procurement expected to finish, and the tunnelling machine likely delivered — with tunnelling scheduled to start in spring 2028.

Over the next few years: construction of the full road and tunnel network, plus associated infrastructure (junctions, approach roads, landscaping, green spaces, wildlife mitigation, active-travel infrastructure).

Assuming all goes to plan, the LTC could open in the early 2030s — fulfilling its promise to relieve congestion east of London, improve connectivity, and deliver a modern, green transport link across the Thames.

Conclusion — A transformational but ambitious bet

The Lower Thames Crossing stands out as one of the boldest — and potentially most beneficial — infrastructure projects in recent UK history. With official planning consent secured in 2025 and procurement of a world-class tunnelling machine under way, the project is entering its most critical phase: construction.

If successful, LTC will bring tangible benefits: faster, more reliable journeys; increased capacity for trade and freight; new green spaces and amenities; and a welcome reduction in pressure on the Dartford Crossing.

Yet the scale, cost, and engineering complexity also make this a massive undertaking — one where delays, cost overruns, or technical challenges remain real possibilities. As such, the next few years will be decisive: for engineers, policymakers, and for communities along the route.

In short: the Lower Thames Crossing is no longer just a plan — it's becoming reality. For further information please visit the tunnelbuider archives. 49/25.