Fix Chevening M25/M26?

[jackal]

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.

Interestingly the clockwise M25 would lose its TOTSO but gain an offside entry from the M26, so not really a net improvement in that respect.

[Richardf]

Looks good, and if we were only having to deal with the M26 and M25 then it would be the best option for the junction, but i cant see how you can easily add in movements for the A21 into such a layout. Unless you have an M1/M25 arrangement, which wouldnt gain anything in terms of A21/Sevenoaks motorway access, and would probably be worse than the current arrangement.

[jackal]

Looks good, and if we were only having to deal with the M26 and M25 then it would be the best option for the junction,

Hardly - the M25 still has two nearside exits and one nearside entry in that design, when ideally it would be the mainline.

but i cant see how you can easily add in movements for the A21 into such a layout. Unless you have an M1/M25 arrangement, which wouldnt gain anything in terms of A21/Sevenoaks motorway access, and would probably be worse than the current arrangement.

Well, the M1/M25 junction is just a stack minus a few ramps, so you could just add in the missing ramps - or to save a bit of money, make one of them a loop. But I agree, it wouldn't exactly be 'easy' - or cheap.

[Richardf]

If you look at the junctions pages on CBRD, there are details on about 3 different designs for a 3 way freeflow junctions. One of those would avoid the problems you describe.

EDIT: A 'semidirectional T ' type junction with a bias toward making the M25 the mainline through the Junction could be designed for the 2 motorways but again, no provision for the A21.

[Chris5156]

If you look at the junctions pages on CBRD, there are details on about 3 different designs for a 3 way freeflow junctions. One of those would avoid the problems you describe.

EDIT: A 'semidirectional T ' type junction with a bias toward making the M25 the mainline through the Junction could be designed for the 2 motorways but again, no provision for the A21.

I can't see how that would be suitable at all - why would you bother providing for turns between the north and east arms? There's no reason for traffic using the M26 to get to or from the north here.

What Chevening needs is the movements that already exist, plus access between the M26 and A21. A three-way junction connecting the M25 and M26 in all directions misses the point.

[jackal]

Consultation to reduce clockwise speed limit within the junction to 50mph:

https://highwaysengland.citizenspace.co ... unction-5/

(Link edited per ABB123.)

[ABB125]

Consultation to reduce clockwise speed limit within the junction to 50mph:

https://highwaysengland.citizenspace.co ... sultation/

That link is for M1 J2.
Here's the correct one:
https://highwaysengland.citizenspace.co ... unction-5/

[Bryn666]

It's a sharp turn for a "mainline" and really nothing to be upset by but I'm sure the ABD and the Mr Toads will be furious at the impingement on their civil liberties.

I came up with an idea to make the M25 a bonafide mainline and allow the missing M26/A21 movements a few pages back. It too would need a 50 limit.

[jackal]

I think that's the best design in the thread actually (possibly I missed it first time round). My quibble with adding A21>M26 was the significant extra expense for a local movement, so it's a stroke of genius to combine it with the new M25>M26 movement. Still there may be an issue with the land take encroaching on local properties but that probably can't be helped.

[Truvelo]

It may be a sharp turn but it's one I can do 70 very comfortably in. Why do we have to keep reducing speed limits to suit the lowest common denominator of driving? It's like Bredbury, before the yellow vultures went up I was easily able to do 70 round there.

As for as Chevening goes, if it's due to merging in heavy traffic then use the variable limits to set it to 50 in the day and NSL at night. Too many measures have been introduced in recent decades in an attempt to deal with heavy traffic only to compromise night driving

[Bryn666]

I think that's the best design in the thread actually (possibly I missed it first time round). My quibble with adding A21>M26 was the significant extra expense for a local movement, so it's a stroke of genius to combine it with the new M25>M26 movement. Still there may be an issue with the land take encroaching on local properties but that probably can't be helped.

Very kind of you - unfortunately we can probably guess that HE, if they ever decide to do anything, will either come up with some kind of misshapen loop like the M25/A12 proposal or insist on 70mph movements so have to scrap both scheme options due to land take issues...

[Bryn666]

It may be a sharp turn but it's one I can do 70 very comfortably in. Why do we have to keep reducing speed limits to suit the lowest common denominator of driving? It's like Bredbury, before the yellow vultures went up I was easily able to do 70 round there.

As for as Chevening goes, if it's due to merging in heavy traffic then use the variable limits to set it to 50 in the day and NSL at night. Too many measures have been introduced in recent decades in an attempt to deal with heavy traffic only to compromise night driving

Centrifugal forces on larger HGVs that throw themselves into a curve at 56, young divs in a car too powerful for their talent level, there are all kinds of substandard drivers - and be wary of falling into the "I can do something so everyone else can" trap, the worst drivers are the complacent bragging ones

[Brenley Corner]

Consultation to reduce clockwise speed limit within the junction to 50mph:

https://highwaysengland.citizenspace.co ... unction-5/

(Link edited per ABB123.)

I cant see an issue with reducing the speed limit here; its only about half a mile so any additional time is only measured in seconds. There have been several accidents here so seems very sensible for very little loss.
It will be much like the short distance of M3 south-westbound at J2 that is 50mph.

Tony

[Nathan_A_RF]

I believe permanent 50 signs have been there for a while now, a good few months. I assume then that was a trial and they are consulting with data they're got?

[John McAdam]

Consultation to reduce clockwise speed limit within the junction to 50mph:

https://highwaysengland.citizenspace.co ... unction-5/

(Link edited per ABB123.)

I cant see an issue with reducing the speed limit here; its only about half a mile so any additional time is only measured in seconds. There have been several accidents here so seems very sensible for very little loss.
It will be much like the short distance of M3 south-westbound at J2 that is 50mph.

Ditto - seems sensible given the geometry of the junction.

Will the westbound carriageway of the M26 be slowed to 50mph coming into the merge - from the right, no less - of the M25 carriageway? It can be a bit disconcerting to be on the westbound M25 joining traffic from the M26 (also w/b) travelling significantly faster to your left - likewise, coming on the M26 westbound it can be a bit alarming to be among that faster traffic merging with the slower M25 flow and watching the potential conflicts as the slower moving M25 traffic filters over to the left hand lanes, whilst some drivers from the M26 just want to charge on through regardless.

[Micro The Maniac]

It's a sharp turn for a "mainline" and really nothing to be upset by but I'm sure the ABD and the Mr Toads will be furious at the impingement on their civil liberties.

Yebbut... whether motorways, truck routes or local roads, it seems the main "safety improvement" tool in the HE box is reductions in speed limits.

It does mean, of course, that HE have recognised that there is a problem here.

Presumably, this will be policed by more yellow vultures (otherwise it will not be, in general, respected). That, at least, should be a nice cash pot to actually fix the problem.

[Peter Freeman]

I think a 50 limit on that curve is a good proposal. It's a very low-cost way to improve safety, with hardly any journey-time effect.

I also agree that the westbound M26 should have an equal limit for the duration of the merge (including the A21 merge).

By the way, why does a 2+2=4 merge require a tiger tail?

[Bryn666]

I think a 50 limit on that curve is a good proposal. It's a very low-cost way to improve safety, with hardly any journey-time effect.

I also agree that the westbound M26 should have an equal limit for the duration of the merge (including the A21 merge).

By the way, why does a 2+2=4 merge require a tiger tail?

I'd say no to the tiger tail question, but they'll have kept this because of how the merge worked before the smart motorway - they'd already eaten the hard shoulder for about 800m to extend the merging area.

[someone]

Presumably, this will be policed by more yellow vultures (otherwise it will not be, in general, respected). That, at least, should be a nice cash pot to actually fix the problem.

When the tabloids like to do their "most lucrative" speed camera stories the one with the highest revenue are around £600k per year. At least one story put the cost of average speed cameras at £100k per mile.

So if you assume half a million pounds a year, it will take a while for the nice pot to be able pay to remodel the junction.

[Micro The Maniac]

At least one story put the cost of average speed cameras at £100k per mile.

How on earth does it cost £100k/mile?

I'd love to see the know the true cost.