M40 - A46 - A429

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Where is it?

Junction diagramM40 junction 15. The London-Birmingham motorway meets the A46, the main road linking Stratford-upon-Avon, Warwick and Coventry. This point is the southern end of the Warwick western bypass.

What's wrong with it?

Yes, it's another overloaded roundabout interchange. Nothing unusual there — we have a three-lane motorway sailing through underneath while all hell lets lose up above. A little way further north-east, the A46 has three lanes each way as well, so it seems a little harsh to just bring it to a halt at the roundabout like this.

Why is it wrong?

This junction is an overloaded roundabout interchange with a twist. Yes, the extra entertainment value here is provided by the junction's history. Not so long ago, the A46 just stopped here at a roundabout, meeting the A429 and the Warwick southern bypass. The A46 was grade-separated already to the north, and this roundabout was built with provision for a flyover. You can still see the flared carriageways today.

In 1991, a cash-strapped government opened the M40 through here. Among other cost saving design points, it ate the existing Warwick southern bypass and ploughed under this roundabout, providing even more interchanging traffic and grade separation in the wrong direction (and indeed, for several years, traffic on the M40 underneath was probably lighter than that round the junction itself).

What would be better?

For a long time this page said that a flyover would be nice, but was unlikely. Well, sometimes dreams come true, and the flyover happened — though, unexpectedly, not neatly across the top of the roundabout as expected. It passes completely north of the existing junction and ends at another, new roundabout to the west. How odd. It has, however, fixed Longbridge Island for the forseeable future and so this poor junction gets a reprieve.

Right to reply

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These are the most recent comments on this junction. You can see all comments if you prefer.

April 2015

Patricia Saville is drawn to the M40:

I hate this island no matter how careful I am I miss the A46 exit and end up going back on to the M40 ugh! It's the only island I have a problem with it just is not signed correctly or road marked correctly.

December 2011

blundelo has no shortage of thoughts:

Generally, the junction functions a lot better since the A46 bridge was opened. However, I exit the southbound M40 to take the A429 northbound into Warwick as part of my daily commute, and often see drivers completely baffled by the lane options available.

The main junction is still traffic-light controlled, but can be bypassed via a filter lane for traffic leaving the M40(S) to join the A46(N), which is obviously not light-controlled (it would be a bit pointless otherwise). However, I often see drivers pull into the filter lane only to stop at the red light, thinking it applies to them despite the lack of a stop line. I've never seen anyone plough straight into the back of a stationary vehicle there, but it's only a matter of time.

Now, on the slip road approaching the junction itself there are two lanes, the right-hand one of which then splits in two to make three lanes in total for the "roundabout". The obvious destination for the left-hand lane would be the A429(N), since the first exit from the roundabout, the A46(N), is already catered for by the aforementioned filter lane.

Obvious, but wrong.

The left-hand lane is also for the A46(N) only, although why anyone would want to wait at the lights to turn left rather than use the filter lane is beyond me. It may be the case that the planners thought that there would be enough traffic to justify having two lanes for A46(N) traffic, but if so, why not just build a two-lane filter - it's already wide enough, with one lane's worth of tarmac covered in hashmarks - and have just two lanes feeding into the roundabout? On the other hand, it may be that the planners feared a lorry might roll over on the filter lane, it is a fairly sharp turn given that it's under national speed limit, but this would seem an extreme case of contingency planning for something that you never want to happen - why not just allow the left-hand lane through the lights to be used for A46(N) traffic in those rare circumstances?

Then, the middle lane: this is for A429(N), no other option given that the left lane is for the A46(N), but this middle lane is also marked and signed for the A46(N), making two light-controlled lanes available for a route that already has a dedicated free-flowing filter lane! Bonkers!

Of course, what happens in practice is that drivers not totally familiar with the junction leave the motorway, see the filter lane for the A46(N) and logically assume that the next lane will be for the A429(N), ignoring the signs and road markings that state "COV ONLY" for the left-hand lane. This means that two lanes of traffic are now fighting for the one available lane on the roundabout with access to the A429(N) into Warwick.

The final (right-hand) lane is for traffic wishing to take both the A429(S) and A46(S). I never see any major issues with this (although I never go that way so wouldn't expect to); however I do frequently see drivers in the (pointless) left-hand lane at the lights cut right across my lane and into the A429(S)/A46(S) lane. Whether this is through confusion, or the belief that they own the road, I couldn't say.

Coming southbound out of Warwick towards the junction on the A429 and heading for the M40(N), the situation seems a lot clearer, the middle lane is the correct one, although the right-hand lane seems, by my observations, to be the M40 lane reserved for BMWs, Mercedes-Benzes, and anyone else whose sense of their own importance is inflated enough to enable them to behave in a fashion which, if they tried it in the Post Office on pension day, would earn them a walking frame to the shinbone.

April 2010

Sam is somewhat relieved:

The traffic on the main island is reasonable now that the bypass has opened, even in rush hour. A huge problem is that a lot traffic uses the M40 between J15 and J14 during rush hour. This stretch is the only way past Warwick to the south - this bit of the M40 was the Warwick southern bypass (as mentioned).

In the morning, the hard shoulder from J15 to J14 is often a fourth lane of queuing traffic - joining the M40 at J15 to head to London requires one to get into the middle lane as soon as possible, dodging M40 traffic cutting over your slip road to join the hard shoulder queue. If you stay in the left lane you need to watch out for traffic trying to join the queue late on.

I can see the above only getting worse now that J15 has improved. I think the M40 needs to be 4 lanes between J15 and J14. No idea if there is any plans for this though.

February 2010

Les is waiting for trouble:

The new bypass is now open, but fairly quiet.

I came south down the A46 onto the M40 North. You are signposted down the new road, over the motorway, left on a hellishly sharp sliproad missing the new island, then onto the main island, then first exit.

I guess this all saves you going all the way around the main island, but I would watch out on the news for the first lorry to fall over on the corner by the new small island.

February 2010

Rob is feeling relieved:

Flyover for A46 through traffic (Stratford <-> Coventry) is now open, and has reduced dramatically the amount of traffic using the main island. The new small roundabout doesn't seem to be causing issues.

One thing that seems a little odd, is that heading south on the A46 towards the junction, the signs for M40(S) send you left to the main junction whilst those for M40(N) send you over the new flyover, then left, left and left again to join the motorway. Maybe this will seem more logical when the roundabout widening is complete (scheduled for mid this year).