Where is it?
Junction 14 of the M11, its northern terminus. It's the point where it meets the A14, a vital east-west route between the M1, M6, East Anglia and Felixstowe. The main road north out of Cambridge, the A1307, joins in here, as well as the A428 heading west to the A1 and Bedford.
What's wrong with it?
The two main routes here are the M11 and A14. The M11 ends nicely, merging into the A14 as it should, but for the main through route the A14 gets pretty lost. It borrows a bit of A1307 to get to the east-west alignment and westbound traffic leaves the main carriageway and uses a one-lane 270 degree sliproad to eventually arrive on the main carriageway again half a mile later on.
If the A14 is to be taken seriously as one of the most important east-west routes in the country, junctions like this one — and other similar masterpieces along the way — simply will not do. There is also the terrifying section between the two loops where northbound to eastbound traffic has to cross westbound to northbound traffic on the same level in a very short weaving section — and it's only a lane wide.
Why is it wrong?
When the junction was built, the A14 simply didn't exist. Going from east to west was the A45, which was the point where the M11 merged into the A604 (which was then the A14 and A1307's north-south alignment). A few connecting sliproads were included to join up all the roads, and all went well, considering the next junction back down the M11 finished off the missing movements.
In the late 1980s, there was a new plan to build the A14 — an east-west arterial route from Felixstowe in the east to the M1/M6 junction in the west — mostly out of bits and pieces of other routes. Part of this plan involved consuming part of the A45 Cambridge northern bypass, and the A604 from the M11 to the A1. The road numbers changed, the main flow of traffic changed with them, but this junction designed when most traffic went straight through stayed exactly as it was.
What would be better?
The very simplest thing to do would be to widen the southbound to eastbound sliproad to two lanes and give it priority at the merge and diverge points. Next up needs to be a much improved link from westbound to to northbound, perhaps taking the entire westbound carriageway over to merge with the M11, leaving A428 or M11 traffic to exit. Then how about upgrading the A14 to the north with a lane or two more?
Right to reply
The most spectacularly broken aspect of this junction is the Girton-to-Madingley bridleway that goes straight through the middle of it.
I've run that route, and would really not like to try to take a horse through it.
It's (necessarily, given motorway restrictions) in underpasses under the M11 and the northwestern looping slip road, but on the other side you get to run across (from recollection) a total of five lanes on three carriageways of very fast road, with an entirely un-signposted (and quite counter-intuitive) direction change from one carriageway to the next to catch you out part way through.
This is probably not the place to rant about the cost-cutting use of on-carriageway footpath and bridleway crossings on the A14...
I actually live in Madingley and I agree with the previous comment - rarely have I ever joined a fast moving A-road from a junction on the right, and then having to go across several lanes in order to come off to go to Madingley (down one of the bumpiest roads in Britain). On a motorbike it can be quite scary as you have very little time to change lanes and the cars on the left come right into your blind spot.
Gosh, you think this design is bad. You should see what they're preparing to build. The A14 northbound is going to become TWO duals; one "stopping" line which goes to the junctions north, the other "express" one doesn't allow interchanges.
Along with commensurate extra sliproads, lane changes and people arriving at the junction unsure of which of the two A14s to use.
And currently we're promised a camera enforced speed limit for 3 years while it's all done...
There are some other aspects to this junction that are particularly special.
The obvious one not already mentioned is that all the long distance A14 traffic westbound heading for either the M11 or A14 W are funnelled down one slip, while the A14 turns into two lanes of A428 which sit obliviously empty. Given the A14 W gets heavily overloaded at Cambridge commuter time, this isn't the best of designs.
Also the junction with The Avenue in Madingley is 'fun'... it's an almost square-on T-junction of a rural road with what's effectively 4 lanes of motorway (though the motorway lanes don't merge until a few hundred yards further on). You get to merge, from a standing start, with heavy traffic doing 70 continuing down the A14.
Though the A14 is particularly fond of rightangled junctions with a tiny sliproad, so perhaps we should be used to it.
Coming along from the East, if you blink it is so easy to end up on the A428 instead of the northbound A14.
I have made that mistake, been in other cars that have done it and heard tales of others doing it.
Once alert to that possibility, it seems ages until you can be sure you're heading along the correct road.
You should be able to purchase special T Shirts, certificates and trophies!
Travelling West along the A14/A428 at night, approaching this junction for the first time, I can only say 'what a nightmare'! Having come up the clover leaf, you have about 100 yards to decide whether Newmarket is East or West (!) and while you are deciding you are being passed at 70 MPH by traffic coming off the M11! You then have another slip road with traffic blinding in from the right and then you find you are thrown into joining the M11 which you know you don't want!! In the short term, traffic signing should be much clearer eg A14 WEST - Midlands, A14 EAST - Felixstowe (which is the regular sign for Eastbound traffic) and signs constantly repeated. Painted signs on the road are often covered. There should be a speed limit on this long sliproad of 50MPH to help matters but it needs additional lanes and improving.
Just been discovered there is a massive void inder this intrchange and is currently being filled before a sink hole appears.