Where is it?
M5 junction 8. The main road south from Birmingham forks, into the M5 (Gloucester, Bristol and the West Country) and the M50 (South Wales).
What's wrong with it?
It's one of these silly ones where a motorway starts at a junction that's anything but free-flowing. The M5 glides across the top on a flyover, while the M50 comes to a grinding halt at the roundabout. Because it's all motorway, the roundabout has hard shoulders and signs saying "Roundabout subject to motorway regulations". It's also a rather disconcerting place to end up when you leave Strensham services heading southbound, since they dump you onto the roundabout too.
Why is it wrong?
There's a good reason why this roundabout interchange makes it into 'Bad Junctions' and all its friends (M18/M180 and so on) don't. The reason is that once upon a time, this junction was free flowing. There was a trumpet interchange here — you can see the empty land where a loop once existed just south-east of the current roundabout. There doesn't seem to be any reason for this; when the M5 north of here was widened from two to three lanes each way, the junction was replaced and made the odd transition away from free-flow. The only imaginable reason is that it eliminates the weaving between the services and the junction by allowing services traffic to join at the junction itself and still access both motorways.
What would be better?
Reinstating the trumpet would be nice, since it's free flow, but this brings back the weaving traffic problem after the services. Since there's not a lot of traffic turning onto the M50 anyway, it's probably not worth changing.
Right to reply
There is an extraordinary vehicles refuge in the centre/East part of the island. This may be the (only) reason why a full roundabout is required at this junction to allow loads to stop when travelling in either direction.
I use this road quite a lot when driving down to see my sister who lives in Swansea. I have never had any problems here because as you say, barely any people ever use the M50. It is however very beautiful.
The worst thing about this junction is the approach from the north for traffic turning west on to M50. There are two exits in very quick succession both appearing on the same ADS. The first exit is for the service area and the second for the turning traffic, only problem is that the second exit taper is so short it is easy to miss if there is slow moving traffic in the left lane. Far better to take all the traffic off at the first slip and abandon the unnecessary complication of two exits.
The services are backwards here. The northbound services should be south of the M50, and the southbound services should be north of it. As it stands, it is impossible to access the services when doing M50 <-> M5 south. This means the only services for people travelling to/from the M50 are Michaelwood, which is an extra 30 miles away, past Gloucester, which can get busy. A 20 mile detour around junction 7 isn't a solution.
This M50/M5 junction actually works quite well; if you consider the "weaving" on the M3 around junctions 11 (uphill), J10 (up/down if exiting NB/joining SB) and j9 (where the A34 comes to a shuddering halt most afternoons other than Christmas day), then the good citizens of Worcestershire have a better (ie SAFER) experience which, let's be honest, adds about a half-minute to the travel time.
Growing up in Somerset in the mid-sixties, our motorway trip to Liverpool started on "the Ross Spur" which we joined one junction to the west, headed to what is now this junction and took the ONLY live exit - northbound towards Birmingham where the M5 ran out (the M5 west of Brum was then a distant planner's dream). Southbound from Strensham, the M5 alignment was just a quiet field.
With the original northbound Strensham services converted into a motorway depot and the "new" Strensham N/B services two miles further north, I reckon this is the best layout that we could hope for.