A Better Solution: Option A14

Our continuing policy is to support a solution that deals fully with the traffic congestion and pollution problems at Dartford, and to deal with them at source. The missing link in the M25, Britain’s busiest motorway, the bottleneck of the Dartford Tunnels must be fixed as soon as possible. Highways England’s own traffic forecasts show that Option C will not fix the problems at Dartford. What is needed is a solution that completes the M25, separates national and regional traffic from local traffic, and which can deal with the pollutants arising from exhaust fumes. The LTCA continues to advocate Option A14, dual motorway grade tunnels from south of Junction 2 to north of Junction 30, thereby removing all M25 through traffic from the existing crossing.

The most rapid, effective and long-lasting improvement to the traffic and pollution problems at Dartford can be effected in the Dartford Crossing corridor.

It appears to the LTCA that many of the route variants within the  Option A corridor have far greater merit than Option C, if evaluated and compared for their environmental benefits, in effecting a sustainable solution to the traffic and pollution problems suffered by Dartford and Thurrock residents. Of the routes at Option A we consider Option A14 to be the most effective in addressing Dartford’s traffic and pollution problems. Option A14 would be a breath of fresh air for Dartford and Thurrock.

We challenge the long-listing and shortlisting decision making process  throughout the consultation.

The following description is taken from Highways England Technical  appraisal Report Volume 2: Existing Conditions and Appraisal of Longlist Options. Report no HA540039- HHJ-ZZZ-REP-ZZZ-009 January 2016.

“Route Option A14 comprises a new route approximately 800m to  the east of the existing QEII Bridge bypassing the existing A282, M25 Junctions 2 and 30. The route would take the form of a 7.4km long dual two-lane bored tunnel with a merge and diverge directly connecting to the mainline M25 south of Junction 2 and north of M25 Junction 30.  The tunnel would be a dual bore until just north of Junction 31 at which point it would become two single bores to pass either side of Junction 30 to then tie-in with the M25 north of Junction 30.”

Option A14 shown as a green dotted line in this diagram from the 2016 Consultation documents

Option A14 Interpretation

Highways England’s documentation says very little about Option A14 so we have to interpret from their brief description what form Option A14 would take. Here’s our take on what Option A14 could look like, based in part on the work of retired Civil Engineer Ken Bowman.


A retired civil engineer has an alternative Option A for the lower Thames Crossing, and it’s supported by Gravesham’s council leader

This article was published on 07 March 2016 during the consultation period.

What needs to happen is a joining on the m25 to the m25, with a six mile tunnel, like they have going underneath Paris. It shouldn’t be beyond us to build a similar tunnel. We just need to go under the whole goddamn lot.”
– Cllr John Cubitt, Leader, Gravesham Borough Council.

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Former civil engineer has an alternative Option A for the lower Thames Crossing, and it’s supported by Gravesham’s council leader
A former chartered civil engineer has come up with an alternative Option A for the lower Thames Crossing. Ken Bowman, now 82, spent years designing tunnels and previously worked on the Victoria tube tunnel and the initial widening of the A2 to make it a dual...

Watch Ken Bowman’s YouTube presentation on Option A14.

A full transcript can be read here.

LTCA Interpretation & Proposal

Whilst the HE document proposes dual two-lane tunnels, LTCA advocates a dual three-lane tunnel crossing.

Our Option A14 proposal would be a 7.4km long dual three-lane bored tunnel with merge and diverge (slip roads) directly connecting to the main M25 south of Junction 2 and north of M25 Junction 30. It would carry all regional and national traffic, including that from the Channel ports, below ground, away from popluated areas in Dartford and by-passing the hot spots of congestion around the exting Dartford-Thurrock Crossing, reducing traffic at the existing crossing by 40% or more, thereby bringing an end to the tailbacks suffered by motorists every day.

The HE document states that their tunnels would be approximately 800m to the east of the existing QEII bridge. The LTCA considers that the position of tunnels relative to surface structures is immaterial to their design. In order to achieve a straighter, and therefore marginally shorter and less costly route alignment, the tunnels could actually pass to the west of the QEII bridge. However, mitigating the risks associated with tunnelling beneath surface structures may dictate the final route.

Option A14 protects far more of the Green Belt than Highways Englands preferred route (Option C). Here you can see how the proposed Option C cuts through vast swathes of Green Belt much of which is also prime agricultural land.

Junction Options

The merge/diverge connections to the mainline M25 shown here has through traffic on the main carriageway while traffic destined for locations in the local Dartford and Thurrock area would exit-left.
Another alternative (shown below) is to give local traffic priority on the main carriageway and have through traffic exit-left. The advantage of this arrangement is that long-distance freight traffic can stay in the far left-hand lanes throughout their journey through the crossing, thereby avoiding congestion caused by lane switching as is evident on the M25 anticlockwise at junction 5 (M26).

Artist’s impression of how the approach to a new Junction 2a providing access to Option A14, dubbed the Dartford Expressway could look.

Tunnels are the Greener Solution

Remember that today’s standards for tunnel construction means they are much taller than the existing Dartford tunnels such that they can carry all traffic at full motorways speeds in a free-flow arrangement.

There is no need for exceptional and hazardous loads to be escorted through these modern-day tunnels.  So the congestion currently experienced at the Dartford Crossing northbound, caused when the traffic is halted to allow for hazardous loads to be escorted, would be a thing of the past for traffic using Option A14.

Examples of free-flow tunnels with no escort arrangement include:

One of the arguments made by oponents of an additional crossing in the Dartford – Thurrock corridor assumes a short bridge or tunnel crossing would be constructed alongside the existing one, as depicted in this map, and therefore critics are concerned about increased congestion, noise and air pollution.  Clearly such a crossing, especially a bridge which would place more traffic in the open air would negatively impact on air quality for residents nearby. There are also difficulties in constructing a new surface crossing because significant traffic management would be required for safety reasons, interrupting and greatly impacting existing traffic flows.

However none of these concerns apply to our Option A14 proposals.

Air extraction and treatment

Tunnels are required to have air extraction and treatment systems that control air quality both inside the tunnel and outside at the discharge points to within acceptable environmental standards.
The longer the tunnel the more exhaust fumes can be captured. Therefore tunnels, especially long ones could actually improve air quality in the Dartford and Thurrock areas.

Advantages of the LTCA Option A14 Proposals

We believe this variant of Route Option A14 would:

  • Reduce traffic on the existing crossing by at least 30% by segregating through traffic into an expressway tunnel
  • Reduce congestion at junctions 2, 1a, 1b, and 30
  • ​Enable improvement of air quality for Dartford through tunnel exhaust containment and treatment
  • ​Free-up the existing crossings for local traffic in Dartford and Thurrock
  • Provide road network resilience in the event of incidents
  • Keep long distance freight traffic contained within the designated route between the channel ports and the north, keeping it off our local roads
The LTCA makes no further claims about the feasibility of this proposal, other than the assumption that it’s inclusion in Highways England’s early longlist of options confirms its technical feasibility.
Tunnel construction could be done entirely off-line from compounds established adjacent to the M25 at junction 2 and junction 30. Construction of the link roads connecting to the proposed tunnels may cause some temporary disruption but no more so than the equivalent links for Option C.
​The link roads involved with this design would be far less damaging to the countryside than those of Option C.
And that’s the tip of the iceberg.  See the information provided in the chart below, which has been extracted from the 2016 Highways England Consultation Pack. Found here > Highways Consultation 2016
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