Fix Chevening M25/M26?

[frediculous_biggs]

If you're going to spend £'s on fixing the TOTSO you might as well provide the A21 to M26 movement. And if you're going to provide this movement you might as well fix the TOTSO. The two go hand in hand.

Except a fairly cheap east facing junction where the A225 crosses the M26 would mean nothing would need to be done for the original junction. Biggest question is: would it be called 2B?

[Stevie D]

Except a fairly cheap east facing junction where the A225 crosses the M26 would mean nothing would need to be done for the original junction. Biggest question is: would it be called 2B?

...or Not 2B?

[Bryn666]

I came up with the following... along similar lines to what has already been considered but without too much additional land take.

https://drive.google.com/open?id=1Ered5 ... sp=sharing

[Richardf]

Jackals plan looks over complicated to me

[ais523]

I came up with the following... along similar lines to what has already been considered but without too much additional land take.

https://drive.google.com/open?id=1Ered5 ... sp=sharing

I was pretty confused with what you'd done for the M25 to M26 link at first, but then I realised that you're using the slip road that my/Truvelo's plan uses for A21 to M26 as an M25 to M26 link too as a method of avoiding the TOTSO without needing additional bridges. That's pretty clever, and something I hadn't thought of. Apart from that, the plan's identical to Truvelo's I think.

[Chris Bertram]

Except a fairly cheap east facing junction where the A225 crosses the M26 would mean nothing would need to be done for the original junction. Biggest question is: would it be called 2B?

...or Not 2B?

If the M26 were to have its own junction numbering scheme, which end would it run from? You could argue either way, and I'd favour going eastbound, like M20.

[Bryn666]

If you have the east facing slips at the A225 you end up going M25 J5, M26 J1, M26 J2, M20 J3, M20 J4.

Perfect!

[Truvelo]

Bryn's design, although space saving, does have a tighter alignment for the M25. As well as removing the TOTSO I feel a smoother alignment is also desirable. I'm wondering if the expense of removing the eastbound TOTSO to create a sharply curved M25 to M26 link is worth it.

As for the A225 junction, is it better than east facing links at Chevening? If most of the M26 bound traffic originates in Sevenoaks then fine but if it comes from further south on the A21 then there will still be traffic cutting through the north of Sevenoaks to get to the A225.

[jackal]

Jackals plan looks over complicated to me

It only looks 'complicated' because it is based around the existing complicated M25 alignment, which reduces disruption, costs and land take. There's not much that's new (red)

[Ritchie333]

From M20E to Tonbridge, the obvious route is via A228 and A26, and Google times the drive from Ashford at 48 minutes. Adding together times for the journey via a direct connector at Chevening comes to 50 minutes. Ashford to Sevenoaks is only a couple of minutes slower coming off onto A25 at Wrotham Heath than via a hypothetical curve at Chevening. The non-motorway alternatives aren't that bad!

I want whatever Google Maps is smoking, because I would be pushed to get from here to Tonbridge in under an hour. Maybe at 2am you can manage it, but not on a Saturday afternoon! The A25 from Wrotham to Sevenoaks is a single carriageway road passing through numerous villages with 30 limits and drops you on the wrong side of Sevenoaks. Similarly, the A228 / A26 combo is okay as far as King's Hill, then it's back down to country lanes with a long 30 stretch through Hadlow village.

A set of east facing sliproads on the A225 would cause problems unless the whole of Chevening was fixed, as everybody would use it to cut the corner between the M26 and A21.

[vlad]

Except a fairly cheap east facing junction where the A225 crosses the M26 would mean nothing would need to be done for the original junction. Biggest question is: would it be called 2B?

J2B would mean it's related to J2A, which could mean the M26 is starting to get junction numbers of its own, which I always thought was against the law. It would need to be J5A or something similar.

[si404]

J2B would mean it's related to J2A, which could mean the M26 is starting to get junction numbers of its own, which I always thought was against the law.

Bursting your bubble, it is the law that provides evidence to the contrary (as J1 and J3 have no off-slips to sign) - 1, 2A, 3.

Therefore an A225 junction would be either 1A or 2.

[Fluid Dynamics]

From M20E to Tonbridge, the obvious route is via A228 and A26, and Google times the drive from Ashford at 48 minutes. Adding together times for the journey via a direct connector at Chevening comes to 50 minutes. Ashford to Sevenoaks is only a couple of minutes slower coming off onto A25 at Wrotham Heath than via a hypothetical curve at Chevening. The non-motorway alternatives aren't that bad!

I want whatever Google Maps is smoking, because I would be pushed to get from here to Tonbridge in under an hour. Maybe at 2am you can manage it, but not on a Saturday afternoon! The A25 from Wrotham to Sevenoaks is a single carriageway road passing through numerous villages with 30 limits and drops you on the wrong side of Sevenoaks. Similarly, the A228 / A26 combo is okay as far as King's Hill, then it's back down to country lanes with a long 30 stretch through Hadlow village.

A set of east facing sliproads on the A225 would cause problems unless the whole of Chevening was fixed, as everybody would use it to cut the corner between the M26 and A21.

I don't agree, apart from the sections between Kings Hill and Mereworth and Colts Hill the A228 is pretty quick. I can at most times of the day get from Tunbridge Wells to Canterbury or Dover in about an hour using A264, A229, M20, A249, M2, A249.

Ashford is either A264, A228, M20 or B2169, A21 (Lamberhurst Bypass), A262, A28 if you don't mind death by a thousand bends.

Didn't the HA develop a scheme for Junction 5 linked to the original (not ALR) M25 J5-6 widening scheme that had new links from the A21 to the M26, via a new link south of the current junction. This would have helped save Riverhead, Seal and Borough Green from some of the traffic that currently uses the the A25 but wouldn't have changed the TOTSO.

As said up post, as a regular user of the junction although an A21 to M26 would be useful, I think the current layout works fine and landownership and topography issues would make most of the fantasy arrangements on here unpalatable, particularly for the residents of Duncton Green who already have their village dissected by the M26.

[Peter Freeman]

Jackals plan looks over complicated to me

It only looks 'complicated' because it is based around the existing complicated M25 alignment, which reduces disruption, costs and land take. There's not much that's new (red)

Yes: simple, easy, NOT cheap fix of TOTSO - but why bother? There are far better uses for the funds.

[Glom]

True. Although TOTSO's get my OCD up, simply cleaning that up with any other gain would be pointless. Unlike the M60 TOTSO where adding a cut-off would be a marked improvement in traffic flow.

[jackal]

It only looks 'complicated' because it is based around the existing complicated M25 alignment, which reduces disruption, costs and land take. There's not much that's new (red)

Yes: simple, easy, NOT cheap fix of TOTSO - but why bother? There are far better uses for the funds.

Although TOTSO's get my OCD up, simply cleaning that up with any other gain would be pointless. Unlike the M60 TOTSO where adding a cut-off would be a marked improvement in traffic flow.

Offside entries/exits generally reduce capacity and safety, and here there's the specific additional issue that it forces the M25 to be reduced to two lanes. If you don't think that has implications for traffic flow that's your problem.

[Bryn666]

There are some implications but the issue has always been the merge.

Now there are four lanes west of J5 the traffic is better. Remember the J3-5 length of the M25 is the quietest section of the entire Orbital so I think delays clockwise due to the diverge are overstated.

As many in Kent will tell you, the problem is the lack of connections rather than the configuration.

[jackal]

There are some implications but the issue has always been the merge.

Now there are four lanes west of J5 the traffic is better. Remember the J3-5 length of the M25 is the quietest section of the entire Orbital so I think delays clockwise due to the diverge are overstated.

As many in Kent will tell you, the problem is the lack of connections rather than the configuration.

It might be the quietest section but it's still at 100k AADF. It's then reduced to effectively 1.5 lanes on the approach to Chevening. Even allowing for 25k or so to/from the A21, 75k into 1.5 lanes (both directions) does not go even in the best of circumstances. And this is far from the best of circumstances, given the right hand exit, which means HGVs for the A21 in lane 2 etc. There's the same basic issue anti-clockwise - the M25 effectively gets 1.5 lanes (a one-lane gain plus a merge with the A21).

At present it's a constraint, but not really a standout one due to the other constraints in either direction, especially around Dartford and J10-16. As these are progressively eased with schemes like the J10-16 smart motorway upgrade, Lower Thames Crossing, and eventually the large scale M25 SW Quadrant scheme, Chevening will grow into a major bottleneck.

Is it a high priority? Not really, right now there are bigger fish to fry. But I think it's clear that in the medium term (RIS 2 or 3) a significant upgrade will be needed here.

I wouldn't rule out the A21-M26 connections getting built 'while they're at it', but local connections like that clearly could not justify the £xxxm expenditure to remodel a major freeflow interchange like this. The main reason to remodel the junction is clearly to improve the flow of the M25 by removing the TOTSOs and increasing the lane allocation.

[lefthandedspanner]

Except a fairly cheap east facing junction where the A225 crosses the M26 would mean nothing would need to be done for the original junction. Biggest question is: would it be called 2B?

...or Not 2B?

If the M26 were to have its own junction numbering scheme, which end would it run from? You could argue either way, and I'd favour going eastbound, like M20.

The distances on the Driver Location Signs increase eastbound and decrease westbound, suggesting the motorway starts at the western end.

Unusually, the main carriageways are marked K and L on those signs instead of the more typical A and B, implying the motorway itself is a sliproad!

[Truvelo]

I've found plans from 1964 for a link road from Dartford Tunnel to the M25 at Sevenoaks. The junction is a three way directional-T with possibly a continuation southwards for the A21 into Sevenoaks. This junction is more restrictive in its movements but does solve the sharp curves on the clockwise M25.