A21 - M25 - M26

Chevening Interchange

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

Martyn Feather 1 March 2006

As you approach the junction, access to the M25 is via the inside lane, which at this point is still full of HGVs heading for the Channel. So it's a slow slog. Or - you could wait to the very end, just when some foreign HGV driver realises he needs to pull out into the middle lane to continue on the M26 - oops too late! Or, as is the case with those unfamiliar with the junction, "surely I don't have to turn off the M25 to stay on the M25?" - "damn... I do!" - and veers straight over the hatched area onto the M25 slip - just. Yep, I've seen all of the above, and they happen on a scarily regular basis.

Finally to cap it all, the slip goes uphill, it divides into two lanes just before the exit. So the inner lane tends to be slow, while the outer is much faster. The inner continues on and becomes the third and innermost lane of what was the two lane A21, whilst the now faster moving traffic feeds into the slower inner lane of the former A21! Great!

Jack Reddall 9 September 2006

Since the opening of the M25/M26/M20 in their entirety, I haven't needed to use the A25, but I decided to stop for dinner at a pub in Brasted on the A25, on my way to Ashford. In 'the old days' I would have had to drive on to Wrotham, and pick up the M20 there, but I thought "ha! There must be a way back onto the motorway system towards Maidstone surely". Not so! Having restarted my journey, I found directions just the other side of Brasted to the M25. Thus began a (short) detour towards the Dartford Crossing, which I was able to remedy at the next exit on the M25. Chastened, I continued (slowly) on the A25 and eventually rejoined the motorway system at Wrotham. Plus ca change, plus c'est la meme chose!

Paul Simons 2 October 2006

Conferring with other drivers complaining about this joke of a junction, try travelling clockwise from Dartford, past the point where the A21 peels off. The "M25" is a twisty two-lane feeder road with a very sharp right hand bend to line it up with the Surrey-bound stretch of the M25. I have seen many vehicles struggle to stay on the road while negotiating this bend. Vehicles then start to accelerate to join the M26. M26 traffic has a straight run through, so is normally travelling faster than traffic on the "M25", meaning that traffic in the left hand lane(s) is travelling faster than traffic in the right hand lanes.

Laurie 8 January 2007

Thank you for highlighting this, the most dangerous junction on the M25. What kind of motorway junction is it where you have to take a slip road to stay on the motorway?

One constantly sees baffled drivers pulling off the straight road at the last minute, having just realised that they are about to be drawn inexorably onto the A21.

It's a killer, and should be fixed pronto.

Craig Morris 8 March 2007

I travel this route quite often and travelling anti-clockwise I agree that the peel off slip road that joins the M25 to the, erm, M25 is confusing to say the least. Get in the inside lane, as prompted by signs, and end up stuck behind a lorry doing 40mph uphill for the next mile until being allowed by road markings to overtake.

Coming clockwise from Dartford, again you have to leave the M25 simply to stay on the road! But worse, when you rejoin after a sweeping right-hand bend you find yourself in the outside lane. Confused? You will be!

Surely any idiot can see that the M25 should be a ring road, and by definition you should be able to go round in circles to your heart's content without having to negotiate dodgy slip roads.

Fabian 22 April 2008

Apart from it being a particularly disastrous junction, what I like about it is that if you get on the A21 at Tonbridge and drive north, and never turn off, after going round the M25, back to this junction for a second time, you eventually end up in Dover.

Ba Storey 23 May 2008

I agree with everything the other commentors have said. What they failed to mention is the impact on the surrounding villages that this lop-sised junction has. Lorries (and anything else) wanting to go to say Sevenoaks town from the coast need to leave the M20 at Wrotham, and travel along the A25 through Borough Green, Seal, Bat and Ball etc. The traffic jams at peak times are horrendous. I have the misfortune to work just outside Sevenoaks, at Sundridge. I travel from West Malling, a journey of 14 miles which usually takes an hour. This is quite ridiculous when I could use M26 all the way. There must be many people like me who waste hours and gallons of petrol in this way, not to mention the impact on the villages. Something must be done.

James 2 November 2009

My mother absolutely hates this junction - even though she remembers it being built and we all know the roads round here like the backs of our collective hands. I tend to agree with her. The worst bit is the "exit" slip road of the clockwise M25 onto the M26-now-turned-M25. You come out and there's simply nowhere to go.

I watch the traffic cameras on trafficengland.com occasionally (boredom) and I've seen more than one overturned lorry taking the road too fast there! It's evidently a nasty place to be, whoever you are...

Tim Shaw 8 February 2010

I could not agree more. What a complete highways fiasco in having 3 main UK highways in Kent unable to properly connect and move UK and European traffic in 2010. The A20, A227, A228 and A25 Kent villages are all suffering a horrendous traffic nightmare because traffic from Europe and East Kent heading towards Tonbridge, Tunbridge Wells, Hastings etc (vice versa) cannot go down the M26 to use the A21.

Catford Cat 20 August 2010

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...

Zakia 8 October 2010

It's such a nightmare, and needs to be dealt with. The junction is built incredibly full of stupidity.

Ron 16 April 2012

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.

Anonymous 6 November 2014

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!

Baldrick 30 December 2014

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.

Robin Desbois 16 September 2017

I agree that this is a horrible design but perhaps part of the problem is that British drivers aren't very used to TOTSO junctions on motorways. They are relatively common here in France, including where two major motorways meet (just look at the A31 junctions with the A6 south and A5 north of Dijon for example). As long as everyone follows the signs rather than GPS instructions, everything seems to work without congestion or accidents.

F.Pitt 24 September 2017

What makes this junction even more ridiculous is that there is a disused railway line that could have been utilsed for traffic wanting to go West on the M26 to South on the A21. In fact, part of the M25 just to the West of this junction does actually use the old railway line for a short stretch - the old Dunton Green to Westerham line.

Charlotte 6 January 2019

Just looking at this junction bothered me, because it could so easily be rebuilt so that the M25 is the through route by building a new mainline along the line of the slip that currently carries the anti-clockwise M25. Otherwise, get rid of the now-redundant clockwise M25 slip and keep the loop from ACW M25 to the A21; CW M25 to A21 is just a simple left-side slip. For access to the M26 from ACW M25, a tunnel could be dug under (or a bridge over) the new M25 mainline. The only tricky bit is getting from the A21 to M25 northwards - now effectively a right turn - and to the M26. A left-turn slip from the M26 to A21, as you say, would be very easy but for those pesky houses in the way. Just a thought, but it might just work.

I agree that the anti-clockwise slip (or M25 east to M25 north) could be widened by another couple of lanes, but why would the clockwise slip coming the other way be redundant?

Keith 10 June 2020

I also dislike how sharp the bend is from M25 Eastbound to A21 (via a very short bit of the M26).

Roads & Maps 21 June 2020

Possibly the scariest Motorway experience I had in the UK. M25 South to M25 West appeared unexpectedly & caused a minor panic.

To rectify the junction, my suggestion is to utilise the existing bridges and build a sweeping new one.
The M25 should continue mainline over the M26 and then (both carriageways) turn West-North West where the current A21 - M25 West sliproad is. The M26 East should remain as such (now a left-turn exit) & the current M26 - M25 West should instead loop around to M25 North. The simple ramp suggested for M26 West - A21 should be built for M26 - M25 West too. Where the current M25 South - West is, a slip should be built for M25 South - M26 East, now essentially creating a trumpet M26 - M25.
Now, the A21 will need to be integrated. By extending the (now former) M25 South - M25 West overpass slip & roadway, this reconfiguration will extend to the A21 South. The existing A21 South mainline will be used as an M26 West - A21 slip, off the M26 - M25 West ramp. The A21 North will now have a simple (replicating, south of the current alignment) slip for A21 - M25 West traffic. And then, the piece de la resistance will be a sweeping overpass from the A21 over the entire thing to M26 East, with a direct M25 North ramp. Alternatively, there could be a loop from A21 North to M26 East, just to the West of Chevening Road, diverging between M26 East and M25 North (using the existing M25 West - North slip) as the A21 squirms under Chevening Road. The (now former) A21 South overpass may need widening for mainline M25 capacity.

Does that work for anyone?

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