The UK is replacing roundabouts with traffic lights; US is doing the opposite

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

by jonathansizz • 11 years ago

49 75 11 years ago

rwmj2• 11 years ago

There seems to be no data supporting the article's assertion that roundabouts are being replaced by traffic lights across the UK as a whole. I'll add my own anecdata: many more roundabouts are being built in my area of the UK. There are also roundabouts with traffic lights.

As a driver, I much prefer roundabouts. When I'm cycling, I just prefer roads with fewer cars and can't wait for self-driving cars, since at least they won't be driven by idiots.

There are safer roundabout designs used in Holland: http://www.aviewfromthecyclepath.com/2014/05/the-best-rounda...

stormcrowsx• 11 years ago

I could see roundabouts being an advantage on smaller one or two lane streets but beyond that it seems like it would get dangerous fast.

hugh4• 11 years ago

It's possible they're both being sensible. Roundabouts are certainly under utilised in the US (unlike those awful four-way stop signs which are particularly hellish for law-abiding cyclists) so putting more in is a good move.

However, as traffic at any particular intersection increases it eventually may make sense to replace a roundabout with a traffic light. Roundabouts can handle large amounts of traffic, but only if they're large roundabouts -- if you can't expand the actual road space then the traffic light is the best move.

phire• 11 years ago

Also, in my experience, roundabouts work best if traffic at all entrances/exits are roughly equal (within an order of magnitude or two)

If traffic flow becomes highly unbalanced, a constant flow of cars from the primary entrance to the primary exit can block all cars from entering the roundabout at secondary entrances. They have to wait for a car to enter at the primary entrance then take the secondary exit so before they can enter.

I was once stuck at a roundabout for 5min due to a sports event in a nearby town creating a constant flow of south to north traffic, when I wanted to go from west to east. The roundabout useally worked perfectly fine, but was broken by the abnormal traffic.

If that intersection had traffic lights, the impact on non south-north traffic would have been minimal.

mixmastamyk2• 11 years ago

The question should be, what is best for this particular intersection in the near future? The two designs have different characteristics.

My understanding is that roundabouts are best when traffic is low, when it gets heavy they become much less efficient. Lights, while a lot of overhead in low traffic, scale better. There's also the question of space required.

Since the UK may have too many roundabouts due to traffic growth, and the US virtually none, they could both be building the opposite and making the right choice.

rwmj2• 11 years ago

The UK also has a lot of roundabouts retrofitted with traffic lights (especially at motorway junctions).

msandford3• 11 years ago

One of the great advantages of roundabouts is that they're approximately "fair" whereas traffic lights are not.

What I mean is that a traffic light is very arbitrary and stops people who just barely didn't make the cutoff. Multiply that by 5, 10, or 20 traffic lights on a journey and an extra minute at each one can add up. So people have incentive to run the light and shave the 30 seconds or a minute. But then when people run the light, it slows down the cross-road who has to wait extra for the road to clear, despite it being "their turn". So then people on that side have an incentive to run the light, because they got wrongfully cutoff by the arbitrariness and the other jerks running the light first. Rinse and repeat for a few cycles and it's easy to see that this is not a good situation.

Traffic circles on the other hand don't suffer from this as there isn't arbitrariness on such a 'long' timescale. If you have to wait for a couple of extra cars it's only a few seconds, versus a minute or so. Because it's just a couple of seconds, people have less to lose and are more inclined to be nice. Which ultimately means that driving is more pleasant, even if it's not as efficient.

I also might disagree with the idea that roundabouts aren't effective at high traffic levels. https://www.youtube.com/watch?v=lwHfibl1AoI

mixmastamyk2• 11 years ago

Not a traffic engineer, but it is what I was told by Kiwis when driving in NZ, and it matched my experience. Driving a particular roundabout was a breeze at lunch (much better typically than a light), but took a very long time just to get into it during the 5pm rush.

Traffic lights have other trade-offs that can be tweaked such as timing length, it is hard to say what is best without knowing more.

jrbancel• 11 years ago

The problem with roundabouts is starvation.

I grew up in France, which has more than 50% of the world's roundabouts. They are everywhere.

Where I am from, there is a roundabout at the intersection of a major road and a small road with little traffic. During rush hour, it is impossible to enter the roundabout coming from the small road because there is a continuous flow of cars coming from the major road. It is truly an uninterrupted flow of cars because the cars come from another roundabout...

Before the roundabout, there was no problem because there was a light that would be always be green for the main road expect when a car was detected on the small road. It was optimal.

suneilp2• 11 years ago

Traffic lights with magnetic sensors to detect cars and amount of cars waiting work pretty well here in California. Unless you're riding a motorcycle...

sliverstorm• 11 years ago

They also seem pretty OK when traffic is moderate, but only in one direction. The minor flow direction pays a price but the dominant flow direction is largely unimpinged compared to a stop light or four-way stop.

toast0• 11 years ago

Lights in low traffic can also be low overhead, if you have adequate sensors. If you only have sensors at the line, and there's a dominant flow, set the dominant flow to green, and cycle through when someone comes up on the non-dominant flow. If you have sensors back far enough, you can leave everyone on red, and cycle to green when someone comes up.

zb• 11 years ago

I don't see roundabouts as a replacement for traffic lights in the US. Above a certain traffic volume, you'll almost always want to move to traffic lights anyway. They're actually a replacement for the 4-way Stop - a ridiculous type of intersection that ought not to exist.

r0m4n0• 11 years ago

Or my personal favorite in Sacramento, roundabout with some stop signs sprinkled in. I hear horns and accidents daily...

https://www.google.com/maps/@38.5801855,-121.4694376,3a,75y,...

fryguy5• 11 years ago

That's not really a roundabout though, it's a traffic circle, which is a replacement for speed bumps. I have one of those near my house in Sacramento as well.

jotux• 11 years ago

Live in Sacramento, the half-roundabouts drive me crazy. Here's another:

https://www.google.com/maps/@38.6759386,-121.5367581,3a,90y,...

function_seven3• 11 years ago

Wait. Is that a 2-way stop? That looks dangerous as hell. If I come upon a stop sign with a island in the middle of the intersection, it is easy to assume that everyone has to stop.

ilyanep• 11 years ago

There are some of these in Palo Alto, as well. I don't think they tend to result in accidents, but I never really understood the point of putting a stop sign on a roundabout.

If I remember correctly, the justification of these here is that they are better for bikes than 4-way stops (which is true, but they're probably not the optimal solution).

https://www.google.com/maps/@37.4420644,-122.1552851,3a,75y,...

verelo2• 11 years ago

Roundabouts with stop signs are insane, i see them in Ontario too and cannot figure them out.

Coming from Australia (that admittedly at times tends to over uses roundabouts) all i can ever wonder when i see a quiet road with traffic lights, or a seemingly pointless 4 way stop sign is "WHY IS THIS NOT A ROUNDABOUT?" I agree at a certain volume there are better alternatives, but there are massive benefits for a very long time and if you have the room for a large enough roundabout they can handle massive volume.

Here is a decent example that is just near Newcastle University in Australia. Traffic lights here would likely be much slower: https://goo.gl/maps/MPhri8vrt5M2

Side note: North America, please stop abusing using "stop" signs. No one stops anyway, just make them "Yield" signs unless its a seriously bad intersection.

Tloewald3• 11 years ago

For true insanity you need to go to Washington DC which has roundabouts with divided lanes, pedestrian crossings, traffic lights, stop signs, and turning lanes.

https://www.google.com/maps/place/Washington,+DC/@38.9092507...

https://www.google.com/maps/place/Washington,+DC/@38.9020455...

mmanfrin• 11 years ago

That's not a roundabout. That is a 2-way stop with a speed-abatement island.

ArtDev• 11 years ago

It depends where you live. Personally, I love roundabouts and so does my city.

tracker1• 11 years ago

Exactly... it's almost an intermediate step... too many locations move from 2/4-way stops straight to lights, when they rarely see enough traffic to really justify it... I think more rural and suburban locations are probably best for this...

If you have more than 2 lanes of traffic in either direction, they're a bad idea... I've seen them used pretty well for certain highway on/off ramps too.

jdc0589• 11 years ago

my city has a few normal roundabouts, and then one insane version where the cars in the roundabout have to yield to people entering. its pretty bad...

ajmurmann2• 11 years ago

There are actually a lot of good cases for roundabout over intersection with traffic lights, but I think that's really something that needs to be decided on a per intersection basis. To me the best replacement for a 4-way stop is really giving one street the right of way and using a yield sign for the less important street. However, that seems to be unheard of in the US.

eridius• 11 years ago

That can make it really hard for the less important street to actually get across, if there are cars coming frequently enough on the more important street. Perhaps more importantly, a yield only works if the yielding street has adequate visibility, and it's primarily only used when merging into a lane (as opposed to crossing an intersection) because trying to keep track of oncoming traffic in both directions and determining when it's safe to cross can be quite hazardous.

In general, the 4-way stop is something that should be rarely used, but is appropriate in some cases. There's a 4-way stop near where I live that I think is very appropriate; the busier road isn't so busy that a stop sign causes traffic to pile up, but is busy enough that if it were given unimpeded flow, the cross street would have difficulty crossing. But installing a traffic light would likely cause longer delays on average for cars, and would also be a bit of a problem as the intersection is at the top of a hill and a traffic light would cause traffic on the main street to back up down the hill (and you don't want people to stop on an uphill if they don't have to).

FWIW, if topography allowed, this would make for a good roundabout spot. But it would take up a bit more space than the (admittedly large) intersection, and the topography of the hill would cause a problem. I suspect that something similar could be said of all appropriate 4-way stop signs, that they'd be better as roundabouts if space and/or topography wasn't a concern.

kazinator3• 11 years ago

4-way Stop - a ridiculous type of intersection that ought not to exist.

Ought not to exist in places like Europe, perhaps.

The four-way stop has the virtue that it is easy for Americans and Canadians to understand.

1. Everyone arriving at the four-way pretends to stop by slowing down to around 20 mph.

2. Regardless of who arrived first, if two or more vehicles take conflicting paths, the biggest asshole goes first. (The algorithm for determining this party takes into account factors such as vehicle size, general socio-economic background, minimum velocity achieved during four-way stop approach, and their apparent perception of where the white stop line is.)

3. When two vehicles take nonconflicting paths (e.g. two directly facing vehicles both go right) they need not acknowledge each others' existence.

4. Only left turns must be indicated. If someone fails to indicate while approaching, they are assumed to be going straight or turning right. Should that be incorrect, the situation is resolved by a fair division of rights: right of way is given to the non-indicating left turner($), whereas the inconvenienced/threatened party is given the right to several prolonged honks of the horn.

5. Where visibility over the other converging roads is not obstructed by building, bush or otherwise, the four-way stop may be completely ignored when not approached by another vehicle with an estimated arrival time that is within a second, either way, of one's own arrival time. (Pedestrians and cyclists may optionally be counted as vehicles at the driver's discretion.)

Who needs roundabouts?

----

$. The governing principle here is consistency -- with rule (2).

herbig• 11 years ago

Where exactly do you live? I've driven all over the east coast and have never, ever seen any of this to be remotely true.

mikestew• 11 years ago

The four-way stop has the virtue that it is easy for Americans and Canadians to understand.

I realize you're being facetious, but that statement is so untrue for the Pacific Northwest of the U. S. that _Portlandia_ even devoted part of an episode to it.

And, surprise, they have trouble with roundabouts, too. Though unlike 4-way stops, it looks like mossbacks are starting to grok roundabouts.

Sanddancer2• 11 years ago

The headline makes it sound like it's a wholesale thing, but from how the article describes it, traffic agencies in both countries are discovering that some intersections are more useful, safer, etc if they had a different kind of traffic control. As information disperses, it becomes easier for engineers from different countries to share ideas and knowledge to figure out what the best course of action is for a certain type of intersection.

vermontdevil• 11 years ago

Wow I can't even. I live in Carmel, IN - basically the roundabout capital of USA. We just built our 100th roundabout and have several more near completion. Love them. Far better than traffic lights.

So weird to see the reason we have them is due to our Mayor visiting England many years ago. Now they are going the other way. Did their mayor or someone visit us and fell in love with traffic lights?

Someone• 11 years ago

"Cyclists have a demonstrably harder time with roundabouts."

As the text acknowledges, a lot depends on the design of the roundabout. Just last week, we got https://bicycledutch.wordpress.com/2015/10/13/explaining-the..., which explains the current thinking of the dutch on roundabout design.

Also, roundabouts have become more popular, but traffic deaths certainly haven't gone up in the Netherlands (https://www.swov.nl/rapport/Factsheets/UK/FS_Road_fatalities...).

malandrew3• 11 years ago

Really? I don't find them challenging at all. Would be even nicer is they put a protected bike ring around the outer edge so cyclists only have to watch out for the part they are crossing across.

chrismealy• 11 years ago

Dutch roundabouts are the best. Lots of videos here:

https://bicycledutch.wordpress.com/tag/roundabout/

sremani• 11 years ago

The overuse of roundabouts is US is in Bend OR. For some reason, I have seen at least half-a-dozen roundabouts there. Most cities, I visited in US have at most a couple of them. Bend OR is roundabout-ville.

ck2• 11 years ago

My town put in a few roundabouts last year and I already noticed memorial flowers at one of them, not sure if for pedestrian, bicycle or car.

shocks• 11 years ago

Here is a particularly terrifying roundabout: https://www.google.co.uk/maps/@51.5628134,-1.7714704,177m/da...

bitwize• 11 years ago

O hai. Welcome to Massachusetts, where the roundabouts have traffic lights, and getting from the Tufts campus to downtown Somerville becomes a game of multidimensional live-action Frogger. And that's if you HAVE a walk signal.

zkhalique• 11 years ago

I think if the roundabouts were large, then in fact they would always be superior to traffic lights. I could probably run the math on that, but the idea is that the lights aren't sensitive to the actual flow of traffic, and often make things backed up for no reason.

josu• 11 years ago

But roundabouts are insensitive to where the traffic is coming from. With light traffic, this is not a problem, but with heavy traffic, if all directions are getting the same priority, it may hurt the entrances with more traffic.

r00fus2• 11 years ago

In France, you see main thoroughfares have overpasses or under-passes and signals into the roundabout that it avoids. Hard to find a map, but essentially, it is to address your concern.

malandrew3• 11 years ago

Strange. I rode the entire PBP (1200km) last month in France and many of the intersections were roundabouts. I didn't see them as any better or worse for cyclists than the 4 way intersections we have today. If anything, it makes it easier for a cyclist to be on the lookout for where a car that could hit them is coming from.

anotherevan• 11 years ago

Comment I'd made[0] on a previous article about roundabouts and their potential for confusion:

I live in Victoria, Australia, and we’ve had roundabouts for ages. I think they are very good for a certain scale of road/traffic. Mostly intersections with moderate amounts of traffic on average, and not high-speed. e.g., the main intersections within housing estates. Having too many of them instead of give-way signs drive you a little batty (I’m looking at you, Warrnambool) while really heavy traffic, major intersections work better with traffic lights.

My daughter recently got her learner license, and she has found roundabouts one of the trickier intersections to navigate. You have to read the traffic flow. This person about to enter on your right is going straight ahead, so will block you entering the roundabout[1], but they have to wait for that person coming the other way from you and going straight through, so you can slip in the gap that creates without cutting anyone else off. As with many things it is familiarity and practice that makes them work[2]. I think roundabouts work very well here for the most part, and my daughter is getting pretty good at reading the traffic. It’s not rocket science[3].

The science of roads and traffic I imagine is a surprisingly nuanced expertise involving a lot of physics and psychology. I find when I cross over the border to New South Wales I feel like a long-tailed cat in a room full of rocking chairs. I eventually figured out it was because the signage was a different distance before the intersection compared to my home state. Once I was aware I could adapt.

[0] https://news.ycombinator.com/item?id=10242816

[1] We drive on the left side of the road because Australia is in the southern hemisphere.

[2] I bet the first traffic lights caused an uproar. “Why the hell should I stop just because there’s a red light?!”

[3] Oh wait, actually, it is rocket science.

ctstover• 11 years ago

I fucking hate roundabouts.

There. I feel better now. Thanks.

Wait, no the rage is coming back - multi-lanes!!! ahhh!! help!

andrewchambers• 11 years ago

Why not have a roundabout with traffic lights on the entrances which are turned on at peak times only to ensure even flow.

dynomight• 11 years ago

I tend to hate roundabouts. They're terrifying. But for 5-ways (and more) I think they can be a better solution than the complicated signage and striping of a traditional intersection. Provided that they are low speed.

There should be a compass marking at the center of each roundabout as standard.

The UK is replacing roundabouts with traffic lights; US is doing the opposite

Related Stories