A21 - M25 - M26
Where is it?
Chevening Interchange, junction 5 of the M25. The point where London's orbital meets the A21, a major route to the south coast, and the M26, a shortcut between the M25 in the south and the M20 towards the Channel Ports.
What's wrong with it?
It appears to have been designed blindfolded. The priority route is M25 to M26 — while a fair amount of traffic does go that way, surely the M25 should have priority over all else, what with it being a ring road to 6 milion people and the busiest road in the country.
Traffic from Sevenoaks is also badly served: to head east from there and join the M26/M20 route, traffic must use the narrow and winding single-carriageway A25 parallel to the M26 since there's no access to the motorway network eastbound from the A21 here. Kent County Council continue to lobby for a change to this situation, all to no avail.
Why is it wrong?
The M25 wasn't meant to be the through route here. The interchange is built around a section of the once-upon-a-time A21 Sevenoaks bypass, which used to be the north-south route here, explaining why that is a mainline carriageway. When the M25 was built, it stopped here, the A21 continuing north and the M26 continuing east. When finally the ends of the M25 were joined up, it was too late, and the junction had to be adapted. The M25 is now carried on little two-lane sliproads.
What would be better?
First of all, let's have access between the A21 and M26 — a left turn M26-A21 is easy enough to add; then A21 to M26 could be achieved by either shifting the north-western sliproad out a bit to make way for a loop, or tunnelling a new sliproad underneath the whole thing (this has been done elsewhere before). As for the M25, how about giving it more lanes and more priority at merges and diverges?
Right to reply
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These are the most recent comments on this junction. You can see all comments if you prefer.
Baldrick has an unusual solution:
Here's an easy fix to this junction: run the M25 on a loop around Sevenoaks. Follow the A25 until the first roundabout, than join the M26 as a T junction. This'll facilitate all the missing movements of the old junction.
It'll be miles cheaper then rebuilding the entire interchange, and Sevenoaks will only be better from it.
This idea uses some very optimistic definitions of the words "easy" and "better"... -Ed.
Having recently driven through this junction, I can certainly say that it is in dire need of major improvement, with the M25 now 4 lanes west of the junction when the 1m ADS appears everyone in lanes 3 and 4 rush to get over to 1 and 2, and the same for traffic wanting the A21/M26. Traffic is squeezed into two lanes for both directions and it's just not enough!
Ron tells a ghost story:
When the A21 Sevenoaks Bypass was built as the earliest component of this nightmare, it was decided that rather than bridge the old railway to Westerham it should be carried across it on an embankment under which was buried the remains of the Chevening railway halt.
As a result the new road was cursed by the ghost of the Ancient Railwayman and will remain cursed until trains run to Westerham once more. Only then will common sense return to the engineers responsible for this stretch of road.
Zakia has only contempt:
It's such a nightmare, and needs to be dealt with. The junction is built incredibly full of stupidity.
Catford Cat writes:
It is kinda crappy, but I think the clockwise approach (i.e. going from Dartford towards Clacket Lane) is simply in need of a sign that says "don't panic, stay in the lane you're in until it all sorts itself out" - if you do that, it isn't a problem. If people suddenly panic at the sight of faster traffic to their left and do something stupid, then it can be...