The Dartford Crossing carries far more traffic than it was designed for, and the long-promised answer is the Lower Thames Crossing (LTC) — a huge new road and tunnel a few miles downstream. After a decade of planning, it received planning permission (a Development Consent Order) in March 2025, and preparation is now under way. This explainer sets out the route, cost, timeline and purpose, and gives an honest view of whether it will fix the Dartford bottleneck. Big infrastructure moves slowly and details change, so treat dates and figures as the position in mid-2026 and check National Highways for the latest.
Key takeaways
- What: a new ~14.3-mile road with twin bored tunnels under the Thames — the UK’s longest road tunnels.
- Where: connecting the A2/M2 in Kent to the M25 and A13 in Essex, east of Dartford.
- Cost: around £10 billion, planned largely through private finance.
- When: permission granted March 2025; construction ramping up through 2026; opening early 2030s.
- Why: to nearly double cross-river road capacity east of London and relieve Dartford.
01 / WHATWhat the Lower Thames Crossing is
The LTC is a new ~14.3-mile (23km) road linking the A2/M2 in Kent to the M25 (around Junction 29) and the A13 in Essex, crossing the Thames through two bored tunnels — one each way — that will be among the largest bored tunnels in the world and the longest road tunnels in the UK. Like the Dartford Crossing, it will use a free-flow charging system (so there’ll be a charge through the tunnel, with no booths). It’s described as the most significant UK road project in a generation.
02 / WHEREThe route & why there
It sits a few miles east (downstream) of the Dartford Crossing, deliberately away from the existing bottleneck so it adds capacity rather than just moving it. On the Kent side it ties into the A2/M2; on the Essex side into the A13 and M25. Several route options were considered over the years, with this alignment chosen to add a genuine second strategic crossing east of London.
03 / COSTCost & how it’s funded
The estimated cost has risen over time to around £10 billion. The government intends to fund it largely through a private-finance model — broadly a mix of public money and a larger private-sector share — with additional public sums committed at the 2025 Autumn Budget and again in mid-2026 for enabling and end-of-tunnel works. As of mid-2026, a private funding partner had not been finalised, so the funding structure is still firming up.
04 / WHENThe timeline
The Development Consent Order was granted in March 2025, after a six-month examination. Since then, advance and enabling works have been under way — utility diversions, ecology and heritage work, and land acquisition. Main construction is expected to ramp up through 2026 (with heavier works following), and delivery partners (Balfour Beatty, Skanska, and a Bouygues–Murphy joint venture) are in place. Build time is estimated at around six years, pointing to an opening in the early 2030s (2032 has been cited). Timelines on projects this size do slip, so treat these as current estimates.
05 / DARTFORDWill it actually ease the Dartford Crossing?
Honestly: it should help, but not soon, and not completely. By nearly doubling cross-river capacity east of London, the LTC is expected to take a large share of traffic — especially freight — off the Dartford Crossing and improve reliability. But it’s years from opening, traffic across the region keeps growing, and some analysts doubt it will fully resolve Dartford’s congestion rather than ease it. In the meantime, the Dart Charge and the Dartford bottleneck are here to stay, so day-to-day it’s business as usual for anyone crossing.
06 / MEANWHILECrossing in the meantime
Until the LTC opens, the practical realities don’t change: pay your Dart Charge on time, expect congestion at peak times, and plan around it. For airport runs across the crossing, a fixed-fare transfer includes the charge and a local driver who knows the crossing’s rhythms. As a Dartford-based, TfL-licensed operator, Rushxo works this crossing every day, LTC or no LTC.
FAQFrequently asked questions
What is the Lower Thames Crossing?
A new ~14.3-mile road linking the A2/M2 in Kent to the M25 and A13 in Essex, crossing the Thames through two bored tunnels — set to be the UK’s longest road tunnels. It’s intended to add a second strategic crossing east of London and relieve the Dartford Crossing.
When will the Lower Thames Crossing open?
Planning permission was granted in March 2025, with construction ramping up through 2026 and a build time of around six years, pointing to an opening in the early 2030s (2032 has been cited). Timelines on projects this size can change.
How much does the Lower Thames Crossing cost?
Around £10 billion on current estimates, planned largely through a private-finance model with a mix of public and private funding. As of mid-2026 a private funding partner had not been finalised.
Where will the Lower Thames Crossing go?
A few miles east (downstream) of the Dartford Crossing, connecting the A2/M2 in Kent to the M25 (around Junction 29) and the A13 in Essex, via twin tunnels under the Thames.
Will the Lower Thames Crossing fix the Dartford Crossing?
It should ease it by nearly doubling cross-river capacity east of London and taking traffic — especially freight — off Dartford. But it’s years from opening, traffic keeps growing, and some doubt it will fully resolve Dartford’s congestion rather than reduce it.
Will the new crossing have a charge like Dart Charge?
Yes — it’s planned to use a free-flow charging system through the tunnel, so there’ll be a charge with no booths, similar in principle to the Dart Charge.
Time Matters
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