'Traffic lights are so dictatorial' ... but are roundabouts on the way out?

[tradephoric]

In response to more cyclists on the road, UK cities are starting to tear out some roundabouts and replace them with traffic signals.  One main reason?  Injuries to cyclists are high at some of these roundabouts.

Inside the Civic Centre of Newcastle City Council, head of transport investment Graham Grant spreads out a map of the city's roads. Accident black-spots are highlighted: an algorithm has ranked roundabouts and junctions according to casualties and injuries. Three roundabouts in the northern Gosforth suburb rank fourth, seventh and 10th worst for injuries caused by motor vehicle collisions. In terms of injuries to cyclists, however, they're one-two-three.

http://www.theguardian.com/cities/2015/oct/19/traffic-lights-roundabouts-way-out

[froggie]

Roundabouts are great for traffic flow.  But not so great when drivers don't yield to bikes/peds...

[silverback1065]

Roundabouts are so so for non motorist traffic, it's nice having an island, but the fact that you don't have to stop when you see a pedestrian, or the fact that drivers don't pay attention, makes for an issue.  I don't see this coming to the US any time soon though, most cities are trying to do the opposite.  I love roundabouts and hate signals though, so I'm biased.  I think it's too easy to add a signal where it's not needed.

[jeffandnicole]

Like all road designs, not every design is suitable for every situation.  And when traffic demands shift, it's normal and proper to see how other road designs could improve traffic flow. 

In other words, welcome to the everyday life of a transportation department.

[vdeane]

Thing is, what the UK calls a "roundabout", we call a rotary.  Our roundabouts are smaller and lower speed, which helps bike/ped use.  Modern ones even include transfer points where bicyclists can switch to the shoulder if they choose, but with the lower speeds, they're generally bike-accessible.  Due to pedestrian issues, the FHWA will be requiring that new multi-lane roundabouts have some form of pedestrian signal (regular signal, HAWK, or the yellow flashing beacons) at the crosswalks.

And you do have to stop when you see a pedestrian, people just don't.

[tradephoric]

Like all road designs, not every design is suitable for every situation.  And when traffic demands shift, it's normal and proper to see how other road designs could improve traffic flow. 

In other words, welcome to the everyday life of a transportation department.

Here's a roundabout in Farndon, UK that was constructed in 2012.  It's pretty shocking that somebody though this rural roundabout was a good idea to build.  You may be giving government agencies too much credit when implying that they are just reacting to changing traffic demands.  Some designs should never have been built in the first place and they are just fixing their self-inflicted boo-boos.  In 2015, this circle underwent a major redesign just a few years after being built.


http://newarkadvertiser.co.uk/articles/news/A46-Farndon-roundabout-layout-will-be-changed

[jakeroot]

Like all road designs, not every design is suitable for every situation.  And when traffic demands shift, it's normal and proper to see how other road designs could improve traffic flow. 

In other words, welcome to the everyday life of a transportation department.

Here's a roundabout in Farndon, UK that was constructed in 2012.  It's pretty shocking that somebody though this rural roundabout was a good idea to build.  You may be giving government agencies too much credit when implying that they are just reacting to changing traffic demands.  Some designs should never have been built in the first place and they are just fixing their self-inflicted boo-boos.  In 2015, this circle underwent a major redesign just a few years after being built.

Is it the size, or the number of lanes that you find shocking? English Si would probably know better than I, but neither seem particularly unique to this roundabout per English standards. I don't think the Highways department would have ever constructed a signal at this intersection (given the rural nature of the area), but I will agree that maybe something a little smaller, with only two lanes would have worked better. Then again, much smaller, and it starts getting difficult to get the side roads to meet properly without a bunch of slip lanes.

This roundabout might be a good candidate for a redesign (either interchange or intersection).

[tradephoric]

^A large roundabout (high circulating speeds) in a rural environment (encourages high speeds) with poor entry deflection angles (encourages high speeds) and marked for 3-lanes (increasing the number of conflict points).  Taken together, that Farndon roundabout is just a failed design.  According to some of the user comments in the article, the roundabout was redesigned in 2015 (removing some circulating lanes).  This redesign took place just 3 years after being built.

[jeffandnicole]

It was also mentioned in the story that at least one approach consisted of 70 mph lanes.

But, as far as your 'giving too much credit to government agencies' comment...there are millions of miles of road, tens of thousands of intersections, thousands of transportation departments, and you try to negate all of that with one example.  You, my friend, are amazing.  Yes, not everything works well, and some designs are head scratchers.  What sounds good in theory may not work well in practice.  But the overwhelming majority of times, it does.

[jakeroot]

^A large roundabout (high circulating speeds) in a rural environment (encourages high speeds) with poor entry deflection angles (encourages high speeds) and marked for 3-lanes (increasing the number of conflict points).  Taken together, that Farndon roundabout is just a failed design.  According to some of the user comments in the article, the roundabout was redesigned in 2015 (removing some circulating lanes).  This redesign took place just 3 years after being built.

I agree with everything except the deflection. The deflection is nothing less than anything you'd see across the UK. The Australian/US-style deflection (with chicanes) is unheard of (except for at least one location). As it exists (now and then), the deflection is perfectly acceptable. Too much chicaning and people don't stay in their lanes, which is more dangerous. The current English style of straight-on then sharp left seems to work fine.

[vdeane]

Technically that thing in Farndon is NOT a roundabout at all.  It's a traffic circle/rotary.  A roundabout is small, can't be traversed at more than ~20 mph (at the MOST; 10-15 mph is more common) and has truck aprons.  More like this: https://www.google.com/maps/@42.7239627,-73.7912535,168m/data=!3m1!1e3

[english si]

Here's a roundabout in Farndon, UK that was constructed in 2012.  It's pretty shocking that somebody though this rural roundabout was a good idea to build.

Why? You want traffic signals when one arm is a 70mph dual carriageway, and another is a 60mph single carriageway? A GSJ wouldn't really work, given the lane drop and high levels of turning traffic. And all a GSJ would do is simply move the problem of a fast trunk road ending at a roundabout one junction further - albeit a roundabout from the 80s that has seen fewer crashes than the modern one.

The concept of a rural, 70mph, 3-lane roundabout isn't the problem here. The problem was shitty engineering.

In 2015, this circle underwent a major redesign just a few years after being built.

Which you cheered as it got rid of a lane.

Sadly it fixed nothing, as the roundabout didn't meet sensible design in the first place with too much deflection, especially on exits (which also narrowed from two lanes to one), and poor signage - both of which were the reasons for the huge accident rate - were left unchanged.

The redesign of this roundabout lead to every DOT employee on SABRE questioning it, as a step sideways at best. The original design was dire and the whole thing spun off into a ranty thread about how a load of highway engineers know nothing. It will be redesigned again at some point in the near future as an old-school style roundabout.

[jakeroot]

...the roundabout didn't meet sensible design in the first place with too much deflection, especially on exits (which also narrowed from two lanes to one)...

Very interesting. So in the UK, is no deflection on exit preferred? I know in the US, deflection on each entry/exit leg is preferred to keep speed down. Then again, too big of a curve hides pedestrians, so I personally prefer a straight exit leg.

It will be redesigned again at some point in the near future as an old-school style roundabout.

Does that mean removing lane lines altogether (instead using arrows prior to entry)? Removing the lane lines at the point where cars cross? I know both are somewhat common in the UK.

Technically that thing in Farndon is NOT a roundabout at all.  It's a traffic circle/rotary.  A roundabout is small, can't be traversed at more than ~20 mph (at the MOST; 10-15 mph is more common) and has truck aprons.  More like this: https://www.google.com/maps/@42.7239627,-73.7912535,168m/data=!3m1!1e3

That's the American definition. The UK definition is much looser. Then again, to me, a roundabout is any circular intersection where traffic entering yields to traffic circulating...size, number of lanes, etc are not relevant (so the Farndon roundabout above is a roundabout, to me). As for trucks aprons, that appears to be more common in North America/Australia, where are trucks are more of the conventional nose-out design. Most of Europe uses cab-over designs, which have much tighter turning radii (plus, places like Germany don't like aprons because of cost and maintenance). But there are still plenty of roundabouts in Europe with aprons, just not at rural roundabouts (the Farndon roundabout would never, ever need an apron).

[riiga]

That's the American definition. The UK definition is much looser. Then again, to me, a roundabout is any circular intersection where traffic entering yields to traffic circulating...size, number of lanes, etc are not relevant (so the Farndon roundabout above is a roundabout, to me).

Seconded. A roundabout in most parts of the world is "any circular intersection where traffic entering yields to traffic circulating".

[noelbotevera]

Roundabout = a circle.

[Scott5114]

Roundabout = a circle.

No. A traffic circle where traffic in the circle must yield to traffic entering the circle is not a roundabout.

[jeffandnicole]

Roundabout = a circle.

No. A traffic circle where traffic in the circle must yield to traffic entering the circle is not a roundabout.

Or there's no specific traffic control whatsoever, as found in many NJ traffic circles.

[BrynM65]

As Si says the example linked is pretty poor; it seems to be a symptom of the UK skills shortage in highway design where people are reading a design manual and not really understanding what they're reading.

A multiple arm roundabout of that size would possibly be given signalised entries to mitigate the deflection issues.

[BrynM65]

Incidentally, the roundabout referred to in the original post at Cowgate was funded as a 'local pinch point' scheme - e.g. signals have been provided to improve side road access as the old roundabout had too much of a dominant flow from the city centre to the A1.

I worked on the Road Safety Audit for it, which if you're building a new road scheme over here you should undertake as routine.

[vdeane]

That's the American definition. The UK definition is much looser. Then again, to me, a roundabout is any circular intersection where traffic entering yields to traffic circulating...size, number of lanes, etc are not relevant (so the Farndon roundabout above is a roundabout, to me).

Seconded. A roundabout in most parts of the world is "any circular intersection where traffic entering yields to traffic circulating".

Let's put it this way.  There are roundabouts and there are traffic circles/rotaries.  One is an innovative intersection type that calms traffic and makes the roads safer, especially for pedestrians/cyclists.  The other is a death trap that isn't built on this side of the pond any more for VERY good reasons.  I'm not sure why the rest of the world doesn't make the distinction.

[jakeroot]

That's the American definition. The UK definition is much looser. Then again, to me, a roundabout is any circular intersection where traffic entering yields to traffic circulating...size, number of lanes, etc are not relevant (so the Farndon roundabout above is a roundabout, to me).

Seconded. A roundabout in most parts of the world is "any circular intersection where traffic entering yields to traffic circulating".

Let's put it this way.  There are roundabouts and there are traffic circles/rotaries.  One is an innovative intersection type that calms traffic and makes the roads safer, especially for pedestrians/cyclists.  The other is a death trap that isn't built on this side of the pond any more for VERY good reasons.  I'm not sure why the rest of the world doesn't make the distinction.

Let's put it another way: American transportation departments don't know how to sign and mark rotaries very well, so they work equally shitty. The rest of the world understands how pavement markings work, so they use them, usually effectively. See these two comparisons, UK left, vs US right...something tells me that the UK does it right (though that image looks a little doctored...allow me to find a better image the roundabout was just recently redesigned).

AFAIC, a roundabout can be any size, as long as it has proper markings and signage.

[Zeffy]

Some actual newer roundabouts in the U.S. are much safer compared to something akin to New Jersey traffic circles and Massachusetts rotaries. Like vdeane said, there is a clear distinction between roundabouts and circles over here. For one, I feel like circles don't have standards - which is why many of them are elliptical or ovular. Roundabouts seem to be near perfect 360 degree circles.

[jakeroot]

Some actual newer roundabouts in the U.S. are much safer compared to something akin to New Jersey traffic circles and Massachusetts rotaries. Like vdeane said, there is a clear distinction between roundabouts and circles over here. For one, I feel like circles don't have standards - which is why many of them are elliptical or ovular. Roundabouts seem to be near perfect 360 degree circles.

But that doesn't have to be so. Sommerville Circle has huge potential, but NJDOT doesn't have any clue how to sign a traffic circle. If they signed it properly, it would be fantastic.

There are some examples of "racetrack" roundabouts in the US: Towson, MD, Santa Barbara, CA, and Colville, WA:

[Zeffy]

But that doesn't have to be so. Somerville Circle has huge potential, but NJDOT doesn't have any clue how to sign a traffic circle. If they signed it properly, it would be fantastic.

You're right, it does have potential. However, it's not just the signing - we also have the issue of not having pavement markings in the circle. This is a bad mistake, because there's no concept of lanes - it's more like "well I think I can be here".

For example:
Brunswick Circle in Trenton, NJ: https://www.google.ca/maps/@40.2451584,-74.7427503,183m/data=!3m1!1e3?hl=en
Flemington Circle in Flemington, NJ: https://www.google.ca/maps/@40.5024394,-74.8535027,217m/data=!3m1!1e3?hl=en
Brooklawn Circle in Brooklawn, NJ: https://www.google.ca/maps/@39.875767,-75.1227327,261m/data=!3m1!1e3?hl=en

Even better is that next to the Flemington Circle, you have this one, which is (IMO) safer than the Flemington Circle solely because the lanes are defined clearly:
https://www.google.ca/maps/@40.5018398,-74.8584492,153m/data=!3m1!1e3?hl=en

[jakeroot]

But that doesn't have to be so. Somerville Circle has huge potential, but NJDOT doesn't have any clue how to sign a traffic circle. If they signed it properly, it would be fantastic.

You're right, it does have potential. However, it's not just the signing - we also have the issue of not having pavement markings in the circle. This is a bad mistake, because there's no concept of lanes - it's more like "well I think I can be here".

Good point. I do realize this, but I forgot to write it. I just kept saying "sign" and "signed" over and over again.

Even better is that next to the Flemington Circle, you have this one, which is (IMO) safer than the Flemington Circle solely because the lanes are defined clearly:
https://www.google.ca/maps/@40.5018398,-74.8584492,153m/data=!3m1!1e3?hl=en

Yes, yes!! Bingo! See, in that case, the size of the roundabout isn't really relevant. There is clearly defined lane lines, yield lines, etc, and the signs, albeit not my favorite, are a step in the right direction towards helping drivers understand their path prior to entry. You could argue that there is some speed issues here, but I don't think that's a big deal, given the good deal of deflection for the entries. At most, drivers are going 25-30 by the time they hit their exit. Slightly faster than the FHWA would prefer but a billion times better than the junk that preceded it.