It's the interchange type everyone loves to hate, but which is the most in need of a major overhaul?

The question focuses on the type of major improvement that really overloaded junctions of this type most often receive. If you think an interchange needs something less substantial, like left turn filters, please vote for something else.

I've only included 'standard' stacked roundabout interchanges, which have a large roundabout positioned above, below or (most commonly) between two mainlines. I've excluded M57/M62, which is already being upgraded. Otherwise every standard stacked roundabout in the UK is, I think, on the list.

EDIT: actually I've somehow ended up leaving A470/A48 off, I guess because it was the last entry on the list I was working on. Is there any way for me to add an answer?

Simister Island, hands down.

Ideally replaced with a completely new junction.

This is no contest, surely? M60/M62/M66 must have by a margin the worst combination of total through traffic on all routes and total traffic using the roundabout part of the interchange.

I'm sure I've mentioned before that Simister was designed to have free-flow links between what is now the two parts of M60 at that junction.

Steven: You may have mentioned it, but I'd still like to hear more!

There's a bit of the M60S near the junction that is kind of flared, but there's no equivalent on the M60W. So would I be right in thinking that the plan involved having the M60S mainline cutting the corner to the M60W, merging with a Y-interchange? Access to the M66 and (via the roundabout) the M62 from the south would be via a separate Y-interchange at the flare.

Or do you mean that provision was made for a freeflow link to go through the junction itself, over or above the roundabout?

I'm also curious as to whether any link would require demolition of the minor road bridge over the M60S or nearby residential properties.

It's a strange geographical anomaly that there aren't any stacked roundabouts north of the M65 near Preston - not a single one in the north east of England or Scotland. Growing up in the north east I thought they were quite exotic and can remember the different route to North Wales we took after the Ferrybridge interchange (old A1/M62) opened in about 1975. Little did I realise the horrors of the overburdened interchanges of the future around the M25.

In fact looking at that list makes you realise that most of the stacked roundabouts were relatively late and not part of the first wave of motorway building. I suppose the earliest on the motorway network was M1/A52. Was that the earliest in the UK or was A41/A406 earlier?

Simister. Needs doing NOW!!!! That roundabout alone has the ability to gridlock half the Greater Manchester motorway network.

OK, right...

Don't forget that the M60 has been widened almost out of all recognition here. You need to look at maps that date to whilst that section of motorway was still M66 (or M68!)

Back then, there was a huge gap between the carriageways. This, as you have supposed would have had been where the slips from the then-M62 to the west would have landed, and would have become the mainline to the south.

These slips would then have "done a Lofthouse" and landed at a fork intersection a little to the west of the roundabout. The difference to Lofthouse is that the slips at Simister woud have been above the junction not below.

There would have been no property destruction at the time, though the modern housing estate to the NW of the junction would have been a couple of houses smaller!

As it happens, a similar solution would have been employed at M62 W <-> M57 S to the east of Liverpool. It's easier in that case to see where the slips would have met the M62 as the Whitefield Lane overbridge is excessively wide...

I'll add the original junction design to the Might Have Been Map when I get the chance if people would like.

It's not that strange. Stacked roundabouts are used where there are two fairly high-capacity roads crossing. With the much lower population density north of the Preston-Leeds-Hull line, it's no great surprise that there aren't so many busy roads needing high(ish) capacity junctions.

In the very early days of building motorways, there were relatively few high-capacity junctions needed, because there were relatively few motorways and major roads. And when land and labour were cheap, it was a lot more affordable and acceptable then to build a large, sprawling, free-flow interchange.

Of course it is. There may be a touch of regional bias, but I'd vote for the M25/A3, M25/A12 and M25/A1(M) junctions before Simister.

P.S. Are there any junctions on this list that you wouldn't want as freeflows? My initial reaction on seeing the list was that, with the exceptions of the M62/A162, A45/A46/A444 and M53/A552, they all need conversion at some point in the future.

A38/A386 is quiet enough to be left alone..though the A386 through the junction is reduced to one-lane resulting in dangerous weaving after the junction. I wonder why this was built as a Stackabout when busier junctions like Marsh Mills are 2-level affairs.

M8/M73 is only missing a couple of slips, but of course it already has its freeflow link from the M8 to M73. We will also be able to count the M74/A725 Raith Interchange in a few years.

Simister without a shadow of doubt.



I am going to have to disagree with you on the A45/A46/A444 junction. Most traffic using this junction is either going A45(W) to A46(S) or A46(N) to A45(E). Do remember that any traffic continuing along the A46 in either direction has to negotiate this junction as the A46 multiplexes with the A45 between this junction and Tollbar located just over a mile to the east.

Same, but when I have passed through this junction it has always felt deserted, except for the A45/6 onslip which somehow manages to be much busier and tight. Don't forget that A46 southbound through traffic already has a bendy filter lane.

"Doing a Lofthouse" here is more of a nice-to-have than a necessity. If I had my way then the A45 would be the through route through Tollbar and the A46 would run between the two junctions on C/D lanes, with both junctions being grade-separated for both A45 and A46 through traffic. Although, if I really got my way then the A46 would run south of Coventry Airport and then up to the M69 on a nice blue line.

Many of these junctions, such as A38/A50 are built and cope fine the way they are because there is very little turning traffic, although my example may change when the services open.

Ah, but Marsh Mills was built twice, so counts double

I voted for Simister but I'd like to see more than just a single additional freeflow added. A freeflow is also needed between Stockport and Leeds in addition to one linking both M60's


There isn't enough space to build C/D roads and make both the A45 and A46 freeflow throughout. The best that can be done is this. The A46 is freeflow throughout but only the westbound A45 is freeflow through Tollbar. The eastbound A45 still has to negotiate the roundabout but with most roundabout traffic removed it shouldn't be busy.
[url=http://www.sabre-roads.org.uk/gallery/albums/userpics/10163/normal_tollbar.jpg"><img src="http://www.sabre-roads.org.uk/gallery/albums/userpics/10163/thumb_tollbar.jpg]http://www.sabre-roads.org.uk/gallery/albums/userpics/10163/normal_tollbar.jpg"><img src="http://www.sabre-roads.org.uk/gallery/albums/userpics/10163/thumb_tollbar.jpg[/url]

I chose Simister island. Like most of you say it needs freeflow! It was much better in the days before the M60!

They're the only four junctions that we've voted for so far. Can we agree that these 4 need fixing ASAP?

I doubt anyone would vote for it anyway, because:
1) It's not that bad -- the limiting factors are probably on the A48 west of there, and on the A470 in both directions (especially the weird merge/diverge with the A469), and the straight-through movements seem much more significant than the turns.
2) There's absolutely no room to do anything there anyway.

If the Llantrisant Radial Road had been built, maybe Gabalfa would be a nightmare.

South Mimms for me. When I returned from England last month I stuck in traffic just once on a 1200 km journey. It was the M25 at South Mimms. So there must be something completely wrong with this junction.