Squareabouts

[martin2345uk]

Junction of A5103 Princess Road with the A57(M) Mancunian Way is squareabout although the entry/exit points are at the corners rather than half way along the sides.

You could call that type a diamond-about.

There's one in Wythenshawe on Hollyhedge Road, or at least used to be.

Do you mean the one on Simonsway that used to be sort of a circle inside a square, before the trams came along and turned it into a signalised crossroads?

[ais523]

They all tend to date from the same era.

Do you know what the design reason was for their popularity at the time? (excepting locations where a squareabout has been constructed to use existing roads, or to fit between obstructions)

According to CBRD, it's because the perfect shape for a roundabout hadn't been figured out yet, and many engineers thought that having actual corners at the exits would be more useful. (The perfect priority rules for a roundabout hadn't been figured out yet either, and when joining traffic isn't forced to give way to circulating traffic, a corner makes much more sense.)

[RichardA626]

You could call that type a diamond-about.

There's one in Wythenshawe on Hollyhedge Road, or at least used to be.

Do you mean the one on Simonsway that used to be sort of a circle inside a square, before the trams came along and turned it into a signalised crossroads?

Yes that's the one, Brownley Road being one of the roads leading off it.

[wrinkly]

Strange that Mancunian Way/Cambridge Street hasn't been mentioned, and A6/A576 in Salford.

[Lheadman]

the "perfect" squareabout has to be in Great Bookham (Surrey). It has been the source of countless comments as to who has right of way and is therefore generally hated but respected as doing what it was intended to do, slow traffic down. Of course it does so by causing total confusion to all who use it, since person A cannot be entirely sure whether person B is going to behave the same way as person A intends to, and therefore lots of near misses and much hooting result.

Even the police have never given a definitive ruling on who has right of way, as shown by several articles in the village mag over the last decade or so.

http://www.geograph.org.uk/photo/56583

[Peter Freeman]

They all tend to date from the same era.

Do you know what the design reason was for their popularity at the time? (excepting locations where a squareabout has been constructed to use existing roads, or to fit between obstructions)

According to CBRD, it's because the perfect shape for a roundabout hadn't been figured out yet, and many engineers thought that having actual corners at the exits would be more useful. (The perfect priority rules for a roundabout hadn't been figured out yet either, and when joining traffic isn't forced to give way to circulating traffic, a corner makes much more sense.)

Before the ''perfect shape" and "perfect priority rules" had been worked out, an earlier theory of large roundabout function prevailed and the square-about was the perfect format for that theoretical model. The idea was that traffic did not need to stop, but could simply (a) perform a side-by-side merge, then (b) weave appropriately on the strait bits, then (c) exit. This theory worked in the many instances (popular in the 1960's) of large gyratories (really just one-way systems) formed from city blocks. It also was deemed to work in some large new-builds at that time. If you examine 1960's futuristic urban road plans (most of which eventually came to nothing) you will see that the square-about, with entry/exit at the corners, was strongly favoured. Ultimately it was displaced by the current geometry.

The current roundabout paradigm does not, usually, employ merging. The give-way at the approach means STOP if there's a vehicle on your right, unless you are SURE that either (a) it's in a right-hand lane and continuing round the roundabout, or (b) you're planning to turn left and he's clearly aiming for the same exit AND staying in his right-hand lane. Since an exit immediately precedes each entry, and modern UK roundabouts tend to operate with quite high speeds, the intentions of circulating vehicles is actually hard to discern until it's too late. Hence the rather inefficient operation of many busy roundabouts. This difficulty of entry leads to the requirement for signalisation of the circulating carriageway and approach-road. And so on, until eventually all the inherent advantages of the brilliant 1960's invention (modern roundabout) have been consumed.

[WHBM]

Various adapted names ("squareabouts", "longabouts") etc can be found to have entered into official parliance, and get used in engineering drawings and notices to the public.

For me Parliament Square, and 1,001 other old urban squares with one way circulation, are not a specifically engineered feature but just a one way system. A squareabout has a 45 degree divergence at each corner entry, and straight intervening sections.

Longabouts have parallel sides and 180 degree curves at each end, with various entries. The classic longabout was for many years (because it has more recently been butchered, several times) The Centre in Bristol, over 1/4 mile end to end, which bus routes in particular used to circulate right around. It had short connectors across the halfway point to save having to go all the way to the end and back again.

[Bryn666]

the "perfect" squareabout has to be in Great Bookham (Surrey). It has been the source of countless comments as to who has right of way and is therefore generally hated but respected as doing what it was intended to do, slow traffic down. Of course it does so by causing total confusion to all who use it, since person A cannot be entirely sure whether person B is going to behave the same way as person A intends to, and therefore lots of near misses and much hooting result.

Even the police have never given a definitive ruling on who has right of way, as shown by several articles in the village mag over the last decade or so.

http://www.geograph.org.uk/photo/56583

That's an unlawful road layout employing give way signs on all arms and some bizarre "feature" that looks likely to kill a motorcyclist one day.

Whoever designed that needs their head banging against the Manual for Streets for the next 600 years.

[FleetlinePhil]

the "perfect" squareabout has to be in Great Bookham (Surrey). It has been the source of countless comments as to who has right of way and is therefore generally hated but respected as doing what it was intended to do, slow traffic down. Of course it does so by causing total confusion to all who use it, since person A cannot be entirely sure whether person B is going to behave the same way as person A intends to, and therefore lots of near misses and much hooting result.

Even the police have never given a definitive ruling on who has right of way, as shown by several articles in the village mag over the last decade or so.

http://www.geograph.org.uk/photo/56583

Odd! It reminds me of this rather unhelpful junction very close to my parents' house, although in this case there is no attempt at providing any form of central marking: https://goo.gl/maps/6fFp1QdStfq. At least this is on relatively lightly-used residential roads, but does still cause confusion and occasional conflict.

EDIT Presumably equally unlawful then, Bryn?

[Bryn666]

Yep. I had this argument when I worked in Blackburn after someone had one reinstated after I took it out following resurfacing.

Apparently they're "safer". Apart from they go against all UK priority rules and generate genuine confusion unlike "excuse confusion" when caught passing a No Entry sign etc. It's a stupid... err... brave and innovative engineer that puts in an unlawful layout and then justifies it with low speed damage collisions are preferable to higher speed injury collisions.

[Ruperts Trooper]

How many Squareabouts are there in the uk and are they actually known by this name
One example is the Gateway Squareabout in Manchester
http://www.sabre-roads.org.uk/wiki/inde ... _20650.jpg

The satnav in my VW uses "square" for junctions it can't figure out or the mapping is out of date - M6>A14 Catthorpe gets the verbal instruction "go straight across the square" !!

[FleetlinePhil]

Yep. I had this argument when I worked in Blackburn after someone had one reinstated after I took it out following resurfacing.

Apparently they're "safer". Apart from they go against all UK priority rules and generate genuine confusion unlike "excuse confusion" when caught passing a No Entry sign etc. It's a stupid... err... brave and innovative engineer that puts in an unlawful layout and then justifies it with low speed damage collisions are preferable to higher speed injury collisions.

I believe it was put in to stop drivers turning left at speed off the B5213 to avoid the traffic lights at the junction with the B5214 and heading straight along Westmorland Road (ie from the left on the GSV). I'm not sure exactly when it was done, but it was like this when I restarted motoring in 2001. At least I now have no reason ever to use it again!

[RichardA626]

There are some dimondabouts in Sharston, on Hollyhedge Road.

[skiddaw05]

Odd! It reminds me of this rather unhelpful junction very close to my parents' house, although in this case there is no attempt at providing any form of central marking: https://goo.gl/maps/6fFp1QdStfq. At least this is on relatively lightly-used residential roads, but does still cause confusion and occasional conflict.

EDIT Presumably equally unlawful then, Bryn?

This looks like (though might not be) something which was once an unmarked junction. These were a feature of my driving lesson routes around King's Lynn a good while ago but now I think they are now simple priority crossroads. Do we still get unmarked junctions anywhere?

[FleetlinePhil]

Odd! It reminds me of this rather unhelpful junction very close to my parents' house, although in this case there is no attempt at providing any form of central marking: https://goo.gl/maps/6fFp1QdStfq. At least this is on relatively lightly-used residential roads, but does still cause confusion and occasional conflict.

EDIT Presumably equally unlawful then, Bryn?

This looks like (though might not be) something which was once an unmarked junction. These were a feature of my driving lesson routes around King's Lynn a good while ago but now I think they are now simple priority crossroads. Do we still get unmarked junctions anywhere?

I do remember dealing with unmarked junctions when learning to drive, there were quite a few around Urmston and Stretford, and some conveniently close to the Test Centre in Whalley Range. I haven't relocated any on GSV, although maybe I'm looking in the wrong places.

However, this was not one of them, well, at least in my lifetime. My recollection was that the priority was previously with Queens Road, part of which can be seen as one-way leading to the junction. This was implemented to make the lights at the B5213/4 junction a 3-way rather than 4-way, but the junction was not marked as it is now at that point. EDIT On further reflection, I think it was actually still two-way from the juction in the GSV to the entrance to the property, with only the actual entrance off the B5213 being one-way.

Perhaps surprisingly, this little section of Queens Road was used as a terminus for the 245/6 local bus services, before they were extended to Altrincham in what turned out to be my last set of bus schedules in 1985. The lay-by is now used for unofficial nose-in parking, much to my annoyance. Prior to it becoming one-way, buses going in the opposite direction (ie towards Flixton or Eccles) used to divert round two sides of this triangle to stand at stops on Queens Road, as the B5213 was not as wide before the junction was rebuilt. There was a building of some sort on the triangle, I think an old Victorian house, up to that date.

[Stevie D]

Odd! It reminds me of this rather unhelpful junction very close to my parents' house, although in this case there is no attempt at providing any form of central marking: https://goo.gl/maps/6fFp1QdStfq. At least this is on relatively lightly-used residential roads, but does still cause confusion and occasional conflict.

Because a mini-roundabout is just too difficult?

[drm567]

the "perfect" squareabout has to be in Great Bookham (Surrey). It has been the source of countless comments as to who has right of way and is therefore generally hated but respected as doing what it was intended to do, slow traffic down. Of course it does so by causing total confusion to all who use it, since person A cannot be entirely sure whether person B is going to behave the same way as person A intends to, and therefore lots of near misses and much hooting result.

Even the police have never given a definitive ruling on who has right of way, as shown by several articles in the village mag over the last decade or so.

http://www.geograph.org.uk/photo/56583

Is this the sort of junction where a 4 way stop could be used, (if it were permitted)? They work well in South Africa, here's an example at Hout Bay, near Cape Town. Though I do wonder if the possibility of the other driver having a 9mm Browning in his glove box concentrates the mind.

[AndyB]

The problem is that crossroads have to have priority marked in some shape or form. Either the main road is marked as such, with a centre white line, or it's blindingly obvious in some other way that the minor roads are of less significance - either they're tiny or there are Give Way or Stop markings.

T junctions and staggered junctions with minor streets (and there are plenty of these in Belfast) might not necessarily merit any form of markings at all if the priority road is of sufficiently low importance (plenty of them in housing developments) because the "straight on" route will always naturally assume precedence.

All-way give ways are totally unnecessary. Mini roundabout (unless hiding behind insufficient room to drive round it on more than two wheels), give the more important road priority, or give the less important road priority as a piece of traffic calming, all are legal and quite proper.

[ajuk]

Surely it wouldn't be that hard to have a free-flowing roundabout that's square with rounded edges, you'd need 3 lanes, 2 approaching and leaving the roundabout on every road, 2 leading to the junction and a 3rd that is only in the roundabout.

The first lane is just a left turn, and if you go into it on the approach you can't then change your mind and go into lane 2, as there's a barrier. Lane 2 is also a left turn, well only if you stay in it, lane 3 is the bit people from lane 2 must merge into if they want to go straight on or right merging back into lane 2 when they get to the appropriate part of the roundabout.

There, sorted it, I squared the circle, free-flowing roundabout, no grade separation, can I have my Nobel Prize?

[Bryn666]

Roundabouts can stop working very quickly if you've got to change lanes or merge in the middle of them.

Decent spiral roundabouts are designed so that you pick a lane before entering and then if any changes are required you move to the right and thus don't merge with anyone and that's a DMRB accepted way of doing things.