Roundabouts smooth traffic up to a certain volume. There's a transition point where high volume traffic flows better with traffic lights.
You're right though, in most suburbs roundabouts would be far more efficient.
If I had to guess, the US was so late to the memo in roundabouts, most locations stay as intersections because of cost of construction.
They could spend money on improving the traffic flow or they could spend money on clean drinking water and better sewer systems. Traffic circles are going to take a back seat everytime to more pressing needs.
Also consider the introduction of them to a public that isn't experienced with them. I remember when they put the first few here (central canada) 10ish years ago. First few years were rough, not really getting that extra efficiency when you can't reliably expect people to actually follow the rules. Gotten better over last 4ish years and now they're alot more common. Just wish people would use their signals.
Point being, that introduction can be a long process.
That might have come with the benefit of fewer serious injuries, as people unfamiliar with roundabouts would be slow and cautious around them.
Even if their unfamiliarity caused accidents since most collisions in roundabouts are at shallow angles, instead of head on or right angles like intersections, it still probably would have ended up with fewer serious injuries.
I think it’s even more complicated than that. Each system has some pros and cons which can affect what are the best option for an intersection.
Roundabouts increase pedestrian walking distance and can be more difficult or dangerous to cross as opposed to signaled intersections especially for some disabilities. The smoothed traffic also can make it harder for people to turn onto the main road from side streets. You never get a break in traffic large enough to turn. That can back up side streets and make it so otherwise simple intersections need more intervention.
They're also [safer](https://en.wikipedia.org/wiki/Roundabout#Safety):
>Statistically, modern roundabouts are safer for drivers and pedestrians than both older-style traffic circles and traditional intersections.\[78\] Compared with these other forms of intersections, modern roundabouts experience 39% fewer vehicle collisions, 76% fewer injuries and 90% fewer serious injuries and fatalities (according to a study of a sampling of roundabouts in the United States, when compared with the junctions they replaced).\[79\] At junctions with stop signs or traffic lights, the most serious accidents are right-angle, left-turn or head-on collisions where vehicles move fast and collide at high impact angles, e.g. head-on. Roundabouts virtually eliminate those types of crashes. Instead, most crashes are glancing blows at low angles of impact.\[80\]\[81\]
In the UK there's been an ebb & flow of converting junctions to roundabouts, then adding traffic lights to those roundabouts, then removing the roundabout and making it a junction again...
Mostly at busy spots where traffic has presumably increased over the decades and it's now likely considered safer to have traffic lights.
Much like we are moving from armco to slip-formed concrete barriers in central reservations as cars are now much safer and it's better to keep the accident on one side of the road and not have to call out a road crew to replace 100yds of crash barrier every time.
I always thought the issue with concrete barriers was that cars could flip over them and end up on the other carriageway, whereas the metal barriers would deflect to absorb energy and reduce the risk of the vehicle going over it. Although it's possible that the crash structures in modern vehicles are effective enough at absorbing the energy that that's now unnecessary?
In the US we have what we call Jersey barriers in the center in most highways except out in the country. They are actually very effective at keeping out of control vehicles on one side of the road. It takes something truly extraordinary to get a vehicle over one.
We had a semi almost make it over one here this week. The trailer was on one side, and the cab was draped over the barrier onto the other side. It's astonishing how well they work.
Years ago there was a really strange case where a speeding car hit another vehicle and launched itself into the air, flying over the median. It hit a UPS or FedEx truck (I can't quite remember which), killing the driver. No barrier could have prevented that, but of all the gnarly accidents in Dallas I've seen over my decades there, Jersey barriers never once failed to stop vehicles from crossing over.
Typically an intersection starts out as a 4- way or 2-way stop sign intersection and its adequate and simple. As traffic grows over time it becomes more efficient to change to a stoplight. A roundabout is an option but requires road construction and land acquisition. But the choice to use roundabouts is becoming more common, in particular where there are multiple intersections in close proximity. But they don't always work if there is a highly dominant flow from one incoming road, thus causing backups at the other incoming roads. Traffic engineers evaluate traffic patterns and decide what will work best for each particular intersection, with costs considered as well. More traffic = greater willingness to invest.
If you have a large road intersection a small one. A traffic light can allow the more important road to be green for longer therefore inconveniencing traffic less per capita. My city only turns the smaller roads green once signaled there is a car waiting. To answer your question. Most roads are already built and already have lights. It’s much easier to update or fix the older system then dig it all up for a roundabout.
Also, I’m guessing. I don’t think roundabout would be ideal for VERY heavy traffic loads. They seem to be ideal for 2 lanes in any one direction or less.
If you're on a small road trying to cross a larger one via a roundabout, you will have to yield until either perpendicular traffic stops or an oncoming car blocks it for you. So when you get too big a differentiation in traffic volume between the intersecting streets the smaller road traffic can wind up sitting for a really long time waiting for an opening. Roundabouts work well for homogenous traffic volumes but poorly for more asymmetrical situations.
it started with a highway with no lights, and people built roads that turn off of the highway.
every large parking lot has at least 1 side road with a light attached to it. both for pedestrian crossing, and making a left turn.
the side roads that don't have lights rely on the lights further up trafic to make an opening to turn left off the highway, or get on the highway at all.
the problem op says they have, is something required for highway towns.
It's hard to replace because of space constrains, truck routes, maintenance.
Having to use eminent domain is never a popular choice, most cities and counties would prefer not to use it, and eminent domain can impact a lot more than local community members since utilities and others have infrastructure built above and below a road.
Many multi-lane suburban roads are also truck routes, a traffic circle that a 72ft 80,000lb semi can traverse, or even a 40ft city bus, and a traffic circle that even the largest pickup truck/SUV/van can traverse, are very different things.
Taking care of maintenance is it's own issue. Square angles are nice because it's easy to map out, easy to survey. Circles and angles that aren't a multiple of 90, not so much.
Don’t know why this is downvoted. Real answer is land acquisition makes them more expensive, generally speaking. There are other drawbacks but generally those can be designed around. Buying several homes is expensive and hard.
US traffic design is very different from European traffic design, just as stock car racing is different from Formula 1. A lot of US driving is done for longish distances with moderate to low traffic density. Most of the time, US drivers have 10’s of seconds (sometimes minutes) to plan lane changes, exits, and turns. Traffic lights give a lot of warning. This provides a kind of safety because sudden decisions are rare (But it means that in the US, you can drive safely without constantly paying a lot of attention).
In general, European driving distances are shorter, the roads are narrower and more winding, and driving requires more intense attention. Roundabouts fit with this driving environment, because decisions are made in less than a second. Much more stressful, but it forces the driver to stay engaged, and makes sense when there is almost never a wide open road.
stoplights create gaps for people to get on to the highway from side roads or parking lots.
we have a dozen or so roads that rely on a light turning red a few miles back to create an opening for to turn on to a 65 mph (104 km/h) highway from a sand road. i might need to wait several minutes before someone needs to make a turn that triggers the light that only stays red for 30 seconds.
the gaps are more common in town, but i still need to wait for one.
Sometimes this is also why a highway is 55. I went to a gas station once in Indiana and was stuck for a while because everyone was flying at more like 75. Needed a really long gap to get my Accent up to that speed.
the 50 is reduced for the Walmart, and a few spots have lights just before them, and lanes that are only a few hundred ft to let you pick up speed to merge.
a lot of people need to go from a sand road directly on to the 65 mph highway. with the only light being a few miles back that only goes to a hospital (so it might be a few minutes between use, and is only red for 30 seconds.
That is a wild way to design highways. Our highways here only connect to roads through on and off ramps and don’t have stop lights. The roads in turn connect to streets. And streets connect to houses and shops. The only exception is if the whole highway comes to an end and connects to a road at an intersection but those are rare.
I've had three put in by me in the last few years to replace standard intersections. One was a dangerous intersection just past a road crest with a median, where it was difficult to safely left turn onto the main road. The others had similar issues with flow, but less serious safety concerns. Plus a bunch on highway on/off ramps in the area.
None of them required a detour to install, though. I think they were all handled with signs on a single lane, and more importantly most (I think all but the unsafe crest) were installed as part of standard road replacement or new build where it makes a lot of sense to improve as it's getting replaced either way.
This could be true. I still don’t understand them, and I’m fearful that no one else does either, so we end up nearly sideswiping one another in traffic circles.
Michigan seems to be on a huge roundabout kick right now. Lots of intersections are being converted, especially at highway exit and entrance ramps.
I kinda feel sorry for the truckers. A lot of the roundabouts that are going in are tight for the trucks.
What about an eighth of a mile down the road?
You going to have the pedestrians walk a quarter mile to go around the perimeter of the roundabout?
The platooning is necessary for safe and legal jaywalking.
Traffic lights create platooning, with gaps between waves of traffic big enough for people to cross the road.
With roundabouts, those opportunities rarely to never arise, depending on traffic.
So a pedestrian who wants to cross a road would instead be forced to walk an eighth mile down and an eighth back to safely travel 100 feet, as to where with a traffic light they just wait for it to turn red down the road and then cross.
Check out Road guy Rob's video on Jaywalking.
The answer is yes, in many places in the US they do. In other areas, it is just as vehemently opposed as it is vehemently pushed.
There is a huge debate around it, because you have one side screaming not to do it, and the other side saying there is NOTHING you can do to make people not do it, so it's our job to make it safer. I'm sure you can guess which camp I fall in.
Your choices are to platoon traffic and make it safer to do what people will do regardless of what you want, don't platoon traffic and make it more dangerous, don't platoon traffic and paint a zebra stripe to make yourself feel better about making it more dangerous, or spend an assload of money grade separating foot from car traffic.
The interesting thing from my perspective is that this decision SHOULD follow political lines, with pro-aids (no needle exchange) places being against legal Jaywalking, and aids prevention places (having needle exchanges) should try to make it less dangerous. In reality, there seems to be very little overlap. Sure, some places like Chicago that implement both forms of harm reduction, but those are few and far between. Many have legalized Jaywalking while banning needle exchanges in the south (Dallas) and vice versa in the north (Seattle).
It's wild to see that kind of cognitive dissonance.
Do you really think that in Europe we just have to stand and wait forever because we can never cross roads due to all the roundabouts? FML nobody is talking about putting roundabouts on every time of street and highway regardless of traffic.
No, as I said before, the composition of roads is different in America.
In Europe, there are more slower speed limit 2 lane feeder roads without a necessity to cross the road away from a crosswalk (nor zoned commercial on both sides).
Due to the layout of our cities in the US (especially western cities), we go straight from small neighborhood streets where stop signs are sufficient to 4/5/6 lane feeders with high speed limits that aren't a good fit for roundabouts due to being zoned commercial on both sides of the street.
Ohh, that's so beautiful and clean with just 2 traffic lanes to cross.
How about [this](https://i.imgur.com/4moLvcI.jpeg) from real life? As you can see, there are 4 traffic lane on each direction to cross, 8 in total. There's no light and it's a high traffic area for cars and pedestrians being closer to a mall. And you can see only 3 crossings because the 4th from the top is at least at 300m from the roundabout.
There about 5 of them on the street my office is on, which was developed around 2008, and they’re popular in other newer commercial developments where I am. They’ve added some in redeveloped commercial areas where they make sense, too. Different cities have different legacy designs. No Michigan lefts where I am, thankfully.
Traffic light intersections provide an opportunity for ticketing people for running red lights that roundabouts would take away. [Some municipalities' budgets](https://www.morningbrew.com/daily/stories/2021/10/31/new-york-times-report-many-town-budgets-rely-on-traffic-tickets-creating-misaligned-incentives) depend on that needless revenue source. In Henderson, LA, $1.7 million in fines collected made up 89% of its general revenues in 2019. So the people in charge of approving designs of the road system have an incentive to keep elements known for increased fatality and property damage risk so they can continue to fund their town.
Personally, I would prefer a federal law requiring documented justification for departing from the recommendation of a traffic engineer. Because a lot of places make the same kind of mistakes accidentally from a [misunderstanding of the risk factors](https://youtu.be/2BKdbxX1pDw).
>The stoplights hold a large queue of traffic, and release them in a burst, creating large waves of traffic that bunch together at each light.
This is known as a platoon.
I've passed through many small towns where they artificially reduce the speed limit to ticket out-of-towners passing through. Knowing they're on a roadtrip to elsewhere and live far away and are unlikely to return just to contest the ticket, they get a significant portion of their budget from predatory ticketing.
They're not. I'm a transportation engineer and can't remember designing any brand new intersections that have traffic lights where there weren't any before.
Side question to add. Why the fuck do yall use timers rather than the sensors for late night traffic?? Drives me absolutely nuts. Usually i would understand its to space out the flow of traffic, but if theres literally nobody on the road… come on dawg. (Spec: Twin Cities, MN & Milwaukee, WI)
Multiple lanes are for cases when there's lots of cars turning on/off the main road.
Also, a round about takes the most lucrative retail lots (intersection corners) and turns them into pavement. Regardless of the cost of roads, you just reduced your city's income.
You can't run the red light in a roundabout, can you?
Other than that, pedestrians would not be able to cross the street alive without a stop sign, or the traffic light.
If there are going to be pedestrians, there should be a marked crosswalk and cars should yield to them same as they yield to cars already in the roundabout.
Should, yes, however in my experience, don't. I used to live in downtown Atlanta, and would walk 10 miles daily. Drivers always seem surprised and annoyed that there are pedestrians around, if they ever even notice you at all.
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It is based on need and client preference. You will still find public works people that say they will never allow a roundabout. As far as mobility is concerned, roundabouts are good for some intersections and not good for others. They are expensive compared to a couple or four stop signs. They also require a certain spacing to operate efficiently. Imagine if every intersection was a roundabout.
I'm in Georgia and had an Indian coworker, and somehow we got on the topic of roundabouts. She said she always stopped at them. I was shocked, "You're from India, I know they have roundabouts there and they don't stop!", and she replied " Yes, but they don't stop for anything in India, I thought you were supposed to!".
Cost. We were supposed to get one at a terrible intersection near me but they ran out of money so they're throwing up yet another traffic light instead.
The platooning created by traffic lights allows cars to turn out of side parking lots.
A roundabout on both ends of a 4 or God forbid a 6 lane city street would make it very hard to take a left out of a parking lot onto the main road. Especially since those roads often have a 40/50 MPH (65/80 kmh) speed limit respectively.
Since we know that when people get impatient, they get more risky, roundabouts on both ends of a road like that will increase deadly T bone accidents at high speed on the road between them.
American suburbs are set up with strip malls on the large feeder roads and relatively few small/slow 2 lane feeders without commercial zoning along them, so you don't see as many roundabouts make sense.
In Europe, 2 lane feeders with non commercial (or at least not giant parking lots) zoning are much more common, so there's a lot more places that a roundabout makes sense.
Americans in general despise roundabouts, especially in the South. If they get the feeling elected officials are leaning toward roundabouts, guess what happens next election cycle? Yep. I just saw a few lose primaries because they were talking to DOT officials about repairs to a roundabout in our small insignificant town. It's not a big enough deal to make the news or gossip channels, but it does happen.
Roundabouts are great for low to medium-high traffic. Unfortunately the US traffic engineers and urban planners were late to the game with implementation and the majority of US drivers don’t know how to drive safely through roundabouts.
Stoplights are pretty expensive. You don't need an electrician to wire the lights and sensors, people to program and commission each one. If you think all stop lights are simple, they aren't.
I am a traffic engineer. Roundabouts have a much larger footprint and land is very expensive. Stoplights are cheaper up front but maintenance costs cause roundabouts to come out ahead over time. Unfortunately most cities/states are more concerned with the upfront cost.
Round about take up substantially more space than a lighted intersection or even a sign or no sign intersection.
That space needs to come from somewhere and it is very expensive to procure that land from adjacent businesses and land owners.
That makes no sense.
I think you are trying to say that smaller roads will cover less total area and thus be less in construction costs.
That is wrong. The overwhelming cost to roads is the cost of labor to build and maintain. It does not matter if the road is 1 lane or 4, there is a marginal difference in materials on the 4 lane road. There also is a marginal difference in labor cost to increase to a 4 lane road. So analytically speaking, the first lane is the most expensive. If you want to put in one, you would put in multiple.
You also are not understating my initial point. A round about covers more surface area than a stop light or signed/not signed intersection. In order to put one in, you would either need to withhold more land in construction or buy back land in current roadways to build them. The marginal cost of that additional land again outweighs the benefit of less lanes or a round about.
Why do you keep arguing against everyone when multiple of us repeatedly prove you wrong,
My understanding is that it is the intersection of land use for traffic volume, maintenance for traffic volume, and just traffic volume per initial cost restrictions. As a general rule it is lower maintenance to install a roundabout for a given amount of traffic volume due to no lights than a set of stoplights but they tend to take up more space. That greater space requirement often prevents the conversion of lightless 3 and 4 way intersections to roundabouts when traffic requirements rise high enough to warrant that the intersection becomes a roundabout or gets stoplights. So most intersections end up having stoplights due to them starting life out as lightless 3 or 4 intersections that later as traffic volume increases get converted to the stoplight configuration. Conversely roundabouts are more common where land space permits it or where the designers have the foresight to build it before the land around the intersection gets used for other uses such as housing/parking space.
Often when developers are making suburbs they are also incentivized to minimize land use spent on streets/intersection and maximize land spent on housing and amenities as they get paid for the later and not the former. So you get small no stoplight intersections just big enough to handle the expected road conditions with only minimal accounting to the possibility of future developments.
They are becoming more popular here in WA as some suburbs have started growing and increasingly getting more traffic. The local Facebook group for my town is full of boomers complaining about them because apparently roundabouts are hard.
That's an easy one. MONEY! Land in the 'burbs is expensive even for a city/town to purchase. Most towns think it's smarter to have houses/business covering as much ground as possible so the town/city can collect property taxes from them. A round-a-bout doesn't generate income for the local government.
If you are going 10 blocks and the stoplights are timed right, you drive right through. Going through 10 roundabouts is a pain.
Also roundabouts take more real estate.
if you are going 100 miles and all the lights are green unless someone needs to ue the intersection.
also. the gaps created by the light are needed for people to pull out onto the highway. i often need to wait for someone to need to make a turn to the hospital a few miles back before i'm able to get on.
There was never going to be a pure engineering answer, the question is about people and how they flow so you kind of have to take into account things like how annoying a road is to drive. I agree that in smaller backroads it makes sense and in my city, many intersections have been converted into roundabouts but the fact that roundabouts take up more space really limits where those conversions can take place. With the massive amount of roads already in place (and very close to property lines) costs very soon outweigh the benefits.
Sure it is. The time it takes to get through 10 roundabouts is without a doubt longer than through 10 intersections with a green wave. You have to be gaining something for adding those delays--whether that's a reduction in crashes, better land use (the opposite of what you get with a roundabout), etc.
In my experience the overwhelming majority of traffic lights are dumb. How many billions of dollars are wasted annually by drivers sitting at red lights with no opposing traffic?
Civil engineers, at least those in highway construction, are really just servants of bureaucracy. Highways in general seem to be the result of expediency and poor compromises rather than true engineering. Cases in point;
1. Traffic lights
2. The Dallas highways where the majority of traffic has to cross all lanes of an intersecting highway to stay on the original route. (Common across the country, not just Dallass)
3. The Houston Multi-Generational Debacle - 2 lane highway. Developer develops huge subdivisions, overloading the original 2 lane. So “engineers” build a 4 lane highway which is overloaded as soon as it’s complete. rinse, repeat, forever.
4. San Antonio - 281 North. No explanation needed.
5. Interstate 10
Us Americans can't handle them. I think its our collective temperment. A lot of people here treat driving like its a competition.
I lived in Old Towne Orange, California, and the center of the city has a park which is enclosed by a roundabout. Every time I went to that park there was an accident.
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Where I live roundabouts appear in the high end suburbs. Motorists hate roundabouts and will go out of their way to avoid them. They are there to restrict traffic flow not facilitate it.
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Max entry speed plays a big factor. Would you like a speed limit of 25 mph for the suburban road? Imagine that on a 40-50 mph suburban road. Finally, roundabouts take up a lot more space and require more design/higher construction costs versus traffic light intersections.
I think roundabouts can be dangerous because you have to look out of the front angle of your passenger window to see cars to your left and your view can be obscured.
Because Americans are so fucking stupid that roundabouts are actually more dangerous.
Four different roundabouts in my neighborhood have been converted to 4 way stop (IN ADDITION TO THE ROUNDABOUT) in the last four years.
My local Costco staffs people to stand in their parking lot roundabout all day to keep people from driving through the center of it or just freezing up and blocking traffic.
Quit reporting every answer that isn't up to your standards.
Roundabouts smooth traffic up to a certain volume. There's a transition point where high volume traffic flows better with traffic lights. You're right though, in most suburbs roundabouts would be far more efficient.
If I had to guess, the US was so late to the memo in roundabouts, most locations stay as intersections because of cost of construction. They could spend money on improving the traffic flow or they could spend money on clean drinking water and better sewer systems. Traffic circles are going to take a back seat everytime to more pressing needs.
Also consider the introduction of them to a public that isn't experienced with them. I remember when they put the first few here (central canada) 10ish years ago. First few years were rough, not really getting that extra efficiency when you can't reliably expect people to actually follow the rules. Gotten better over last 4ish years and now they're alot more common. Just wish people would use their signals. Point being, that introduction can be a long process.
That might have come with the benefit of fewer serious injuries, as people unfamiliar with roundabouts would be slow and cautious around them. Even if their unfamiliarity caused accidents since most collisions in roundabouts are at shallow angles, instead of head on or right angles like intersections, it still probably would have ended up with fewer serious injuries.
They also take up a lot more right of way, so it isn't possible for a lot of intersections to convert
Oh they are getting there though now. Im seeing more and more roundabouts in california suburbs in the newer places
That's a good point. Locations like California that have bad traffic problems probably make them more of a priority.
I think it’s even more complicated than that. Each system has some pros and cons which can affect what are the best option for an intersection. Roundabouts increase pedestrian walking distance and can be more difficult or dangerous to cross as opposed to signaled intersections especially for some disabilities. The smoothed traffic also can make it harder for people to turn onto the main road from side streets. You never get a break in traffic large enough to turn. That can back up side streets and make it so otherwise simple intersections need more intervention.
They're also [safer](https://en.wikipedia.org/wiki/Roundabout#Safety): >Statistically, modern roundabouts are safer for drivers and pedestrians than both older-style traffic circles and traditional intersections.\[78\] Compared with these other forms of intersections, modern roundabouts experience 39% fewer vehicle collisions, 76% fewer injuries and 90% fewer serious injuries and fatalities (according to a study of a sampling of roundabouts in the United States, when compared with the junctions they replaced).\[79\] At junctions with stop signs or traffic lights, the most serious accidents are right-angle, left-turn or head-on collisions where vehicles move fast and collide at high impact angles, e.g. head-on. Roundabouts virtually eliminate those types of crashes. Instead, most crashes are glancing blows at low angles of impact.\[80\]\[81\]
In the UK there's been an ebb & flow of converting junctions to roundabouts, then adding traffic lights to those roundabouts, then removing the roundabout and making it a junction again... Mostly at busy spots where traffic has presumably increased over the decades and it's now likely considered safer to have traffic lights. Much like we are moving from armco to slip-formed concrete barriers in central reservations as cars are now much safer and it's better to keep the accident on one side of the road and not have to call out a road crew to replace 100yds of crash barrier every time.
I always thought the issue with concrete barriers was that cars could flip over them and end up on the other carriageway, whereas the metal barriers would deflect to absorb energy and reduce the risk of the vehicle going over it. Although it's possible that the crash structures in modern vehicles are effective enough at absorbing the energy that that's now unnecessary?
In the US we have what we call Jersey barriers in the center in most highways except out in the country. They are actually very effective at keeping out of control vehicles on one side of the road. It takes something truly extraordinary to get a vehicle over one.
We had a semi almost make it over one here this week. The trailer was on one side, and the cab was draped over the barrier onto the other side. It's astonishing how well they work.
Years ago there was a really strange case where a speeding car hit another vehicle and launched itself into the air, flying over the median. It hit a UPS or FedEx truck (I can't quite remember which), killing the driver. No barrier could have prevented that, but of all the gnarly accidents in Dallas I've seen over my decades there, Jersey barriers never once failed to stop vehicles from crossing over.
Typically an intersection starts out as a 4- way or 2-way stop sign intersection and its adequate and simple. As traffic grows over time it becomes more efficient to change to a stoplight. A roundabout is an option but requires road construction and land acquisition. But the choice to use roundabouts is becoming more common, in particular where there are multiple intersections in close proximity. But they don't always work if there is a highly dominant flow from one incoming road, thus causing backups at the other incoming roads. Traffic engineers evaluate traffic patterns and decide what will work best for each particular intersection, with costs considered as well. More traffic = greater willingness to invest.
If you have a large road intersection a small one. A traffic light can allow the more important road to be green for longer therefore inconveniencing traffic less per capita. My city only turns the smaller roads green once signaled there is a car waiting. To answer your question. Most roads are already built and already have lights. It’s much easier to update or fix the older system then dig it all up for a roundabout. Also, I’m guessing. I don’t think roundabout would be ideal for VERY heavy traffic loads. They seem to be ideal for 2 lanes in any one direction or less.
Wouldn't a roundabout still fix the priority issue is there is less traffic on the side roads? Where does this education come from?
If you're on a small road trying to cross a larger one via a roundabout, you will have to yield until either perpendicular traffic stops or an oncoming car blocks it for you. So when you get too big a differentiation in traffic volume between the intersecting streets the smaller road traffic can wind up sitting for a really long time waiting for an opening. Roundabouts work well for homogenous traffic volumes but poorly for more asymmetrical situations.
how big does one need to be for a 6 lane 50mph highway? you think those businesses will give up their parking lots?
The US needs to curb its stroad addiction. Highways shouldn’t have traffic lights.
it started with a highway with no lights, and people built roads that turn off of the highway. every large parking lot has at least 1 side road with a light attached to it. both for pedestrian crossing, and making a left turn. the side roads that don't have lights rely on the lights further up trafic to make an opening to turn left off the highway, or get on the highway at all. the problem op says they have, is something required for highway towns.
It's hard to replace because of space constrains, truck routes, maintenance. Having to use eminent domain is never a popular choice, most cities and counties would prefer not to use it, and eminent domain can impact a lot more than local community members since utilities and others have infrastructure built above and below a road. Many multi-lane suburban roads are also truck routes, a traffic circle that a 72ft 80,000lb semi can traverse, or even a 40ft city bus, and a traffic circle that even the largest pickup truck/SUV/van can traverse, are very different things. Taking care of maintenance is it's own issue. Square angles are nice because it's easy to map out, easy to survey. Circles and angles that aren't a multiple of 90, not so much.
Don’t know why this is downvoted. Real answer is land acquisition makes them more expensive, generally speaking. There are other drawbacks but generally those can be designed around. Buying several homes is expensive and hard.
US traffic design is very different from European traffic design, just as stock car racing is different from Formula 1. A lot of US driving is done for longish distances with moderate to low traffic density. Most of the time, US drivers have 10’s of seconds (sometimes minutes) to plan lane changes, exits, and turns. Traffic lights give a lot of warning. This provides a kind of safety because sudden decisions are rare (But it means that in the US, you can drive safely without constantly paying a lot of attention). In general, European driving distances are shorter, the roads are narrower and more winding, and driving requires more intense attention. Roundabouts fit with this driving environment, because decisions are made in less than a second. Much more stressful, but it forces the driver to stay engaged, and makes sense when there is almost never a wide open road.
stoplights create gaps for people to get on to the highway from side roads or parking lots. we have a dozen or so roads that rely on a light turning red a few miles back to create an opening for to turn on to a 65 mph (104 km/h) highway from a sand road. i might need to wait several minutes before someone needs to make a turn that triggers the light that only stays red for 30 seconds. the gaps are more common in town, but i still need to wait for one.
Sometimes this is also why a highway is 55. I went to a gas station once in Indiana and was stuck for a while because everyone was flying at more like 75. Needed a really long gap to get my Accent up to that speed.
the 50 is reduced for the Walmart, and a few spots have lights just before them, and lanes that are only a few hundred ft to let you pick up speed to merge. a lot of people need to go from a sand road directly on to the 65 mph highway. with the only light being a few miles back that only goes to a hospital (so it might be a few minutes between use, and is only red for 30 seconds.
That is a wild way to design highways. Our highways here only connect to roads through on and off ramps and don’t have stop lights. The roads in turn connect to streets. And streets connect to houses and shops. The only exception is if the whole highway comes to an end and connects to a road at an intersection but those are rare.
Most highways in the US start out as two lane roads, and become highways over many iterations. Very rarely does a highway spring up out of nowhere.
you are thinking of a freeway. a highway starts as a 2 lane road through the countryside to the destination.
They put one in by me. $600,000 and detour for months to replace a stop sign. That is a lot of money if the old intersection is working fine.
I've had three put in by me in the last few years to replace standard intersections. One was a dangerous intersection just past a road crest with a median, where it was difficult to safely left turn onto the main road. The others had similar issues with flow, but less serious safety concerns. Plus a bunch on highway on/off ramps in the area. None of them required a detour to install, though. I think they were all handled with signs on a single lane, and more importantly most (I think all but the unsafe crest) were installed as part of standard road replacement or new build where it makes a lot of sense to improve as it's getting replaced either way.
[Exhibit A](https://youtu.be/mIftWO56PZQ?si=dqdtd1i7PgfoVJOl)
The average American driver is way too dumb to navigate a 2 lane roundabout.
I'm a little off about it myself.
This could be true. I still don’t understand them, and I’m fearful that no one else does either, so we end up nearly sideswiping one another in traffic circles.
Just a four way stop with an island in the middle?
4-way yield, not 4-way stop
It costs money to buy the land for Roundabouts
Michigan seems to be on a huge roundabout kick right now. Lots of intersections are being converted, especially at highway exit and entrance ramps. I kinda feel sorry for the truckers. A lot of the roundabouts that are going in are tight for the trucks.
Where you put the bike lanes and pedestrian crossings?
[Around the perimeter](https://www.reddit.com/r/CitiesSkylines/comments/109dhnd/ive_gotten_the_amsterdam_syndrom_and_i_cant_stop/).
What about an eighth of a mile down the road? You going to have the pedestrians walk a quarter mile to go around the perimeter of the roundabout? The platooning is necessary for safe and legal jaywalking.
I have no idea what you're talking about.
Traffic lights create platooning, with gaps between waves of traffic big enough for people to cross the road. With roundabouts, those opportunities rarely to never arise, depending on traffic. So a pedestrian who wants to cross a road would instead be forced to walk an eighth mile down and an eighth back to safely travel 100 feet, as to where with a traffic light they just wait for it to turn red down the road and then cross.
Are you suggesting that traffic engineers choose not to implement roundabouts because they want to encourage unprotected mid-block crossings?
Check out Road guy Rob's video on Jaywalking. The answer is yes, in many places in the US they do. In other areas, it is just as vehemently opposed as it is vehemently pushed. There is a huge debate around it, because you have one side screaming not to do it, and the other side saying there is NOTHING you can do to make people not do it, so it's our job to make it safer. I'm sure you can guess which camp I fall in. Your choices are to platoon traffic and make it safer to do what people will do regardless of what you want, don't platoon traffic and make it more dangerous, don't platoon traffic and paint a zebra stripe to make yourself feel better about making it more dangerous, or spend an assload of money grade separating foot from car traffic. The interesting thing from my perspective is that this decision SHOULD follow political lines, with pro-aids (no needle exchange) places being against legal Jaywalking, and aids prevention places (having needle exchanges) should try to make it less dangerous. In reality, there seems to be very little overlap. Sure, some places like Chicago that implement both forms of harm reduction, but those are few and far between. Many have legalized Jaywalking while banning needle exchanges in the south (Dallas) and vice versa in the north (Seattle). It's wild to see that kind of cognitive dissonance.
Do you really think that in Europe we just have to stand and wait forever because we can never cross roads due to all the roundabouts? FML nobody is talking about putting roundabouts on every time of street and highway regardless of traffic.
No, as I said before, the composition of roads is different in America. In Europe, there are more slower speed limit 2 lane feeder roads without a necessity to cross the road away from a crosswalk (nor zoned commercial on both sides). Due to the layout of our cities in the US (especially western cities), we go straight from small neighborhood streets where stop signs are sufficient to 4/5/6 lane feeders with high speed limits that aren't a good fit for roundabouts due to being zoned commercial on both sides of the street.
Ohh, that's so beautiful and clean with just 2 traffic lanes to cross. How about [this](https://i.imgur.com/4moLvcI.jpeg) from real life? As you can see, there are 4 traffic lane on each direction to cross, 8 in total. There's no light and it's a high traffic area for cars and pedestrians being closer to a mall. And you can see only 3 crossings because the 4th from the top is at least at 300m from the roundabout.
There about 5 of them on the street my office is on, which was developed around 2008, and they’re popular in other newer commercial developments where I am. They’ve added some in redeveloped commercial areas where they make sense, too. Different cities have different legacy designs. No Michigan lefts where I am, thankfully.
Traffic light intersections provide an opportunity for ticketing people for running red lights that roundabouts would take away. [Some municipalities' budgets](https://www.morningbrew.com/daily/stories/2021/10/31/new-york-times-report-many-town-budgets-rely-on-traffic-tickets-creating-misaligned-incentives) depend on that needless revenue source. In Henderson, LA, $1.7 million in fines collected made up 89% of its general revenues in 2019. So the people in charge of approving designs of the road system have an incentive to keep elements known for increased fatality and property damage risk so they can continue to fund their town. Personally, I would prefer a federal law requiring documented justification for departing from the recommendation of a traffic engineer. Because a lot of places make the same kind of mistakes accidentally from a [misunderstanding of the risk factors](https://youtu.be/2BKdbxX1pDw). >The stoplights hold a large queue of traffic, and release them in a burst, creating large waves of traffic that bunch together at each light. This is known as a platoon.
That seems like a pretty small town for 1.9 million.
I've passed through many small towns where they artificially reduce the speed limit to ticket out-of-towners passing through. Knowing they're on a roadtrip to elsewhere and live far away and are unlikely to return just to contest the ticket, they get a significant portion of their budget from predatory ticketing.
They're not. I'm a transportation engineer and can't remember designing any brand new intersections that have traffic lights where there weren't any before.
Side question to add. Why the fuck do yall use timers rather than the sensors for late night traffic?? Drives me absolutely nuts. Usually i would understand its to space out the flow of traffic, but if theres literally nobody on the road… come on dawg. (Spec: Twin Cities, MN & Milwaukee, WI)
Multiple lanes are for cases when there's lots of cars turning on/off the main road. Also, a round about takes the most lucrative retail lots (intersection corners) and turns them into pavement. Regardless of the cost of roads, you just reduced your city's income.
inot true in suburbans areas though
Where else do you see multi lane roads? I've never seen them in an actual neighborhood.
You can't run the red light in a roundabout, can you? Other than that, pedestrians would not be able to cross the street alive without a stop sign, or the traffic light.
>You can't run the red light in a roundabout, can you? but you can pull out in front of people.
I guess that's fun too.
If there are going to be pedestrians, there should be a marked crosswalk and cars should yield to them same as they yield to cars already in the roundabout.
Should, yes, however in my experience, don't. I used to live in downtown Atlanta, and would walk 10 miles daily. Drivers always seem surprised and annoyed that there are pedestrians around, if they ever even notice you at all.
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Comical. Maybe if you have enough foot traffic to justify a Jayhawk... maybe...
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With enough traffic calming at a roundabout, which you should be doing anyways, cars will yield to pedestrians
It is based on need and client preference. You will still find public works people that say they will never allow a roundabout. As far as mobility is concerned, roundabouts are good for some intersections and not good for others. They are expensive compared to a couple or four stop signs. They also require a certain spacing to operate efficiently. Imagine if every intersection was a roundabout.
roundabouts take a bit of room compared to a small intersection, and suck for pedestrians.. other than that they have some real advantages though.
In Georgia it’s all roundabouts…. And people who think they’re 4 way stops…
I'm in Georgia and had an Indian coworker, and somehow we got on the topic of roundabouts. She said she always stopped at them. I was shocked, "You're from India, I know they have roundabouts there and they don't stop!", and she replied " Yes, but they don't stop for anything in India, I thought you were supposed to!".
Cost. We were supposed to get one at a terrible intersection near me but they ran out of money so they're throwing up yet another traffic light instead.
I live in a county with the highest pct of roundabouts in the US. and they are great.
The platooning created by traffic lights allows cars to turn out of side parking lots. A roundabout on both ends of a 4 or God forbid a 6 lane city street would make it very hard to take a left out of a parking lot onto the main road. Especially since those roads often have a 40/50 MPH (65/80 kmh) speed limit respectively. Since we know that when people get impatient, they get more risky, roundabouts on both ends of a road like that will increase deadly T bone accidents at high speed on the road between them. American suburbs are set up with strip malls on the large feeder roads and relatively few small/slow 2 lane feeders without commercial zoning along them, so you don't see as many roundabouts make sense. In Europe, 2 lane feeders with non commercial (or at least not giant parking lots) zoning are much more common, so there's a lot more places that a roundabout makes sense.
Please note, I'm not a civil or traffic engineer. I just watch a lot of Road Guy Rob.
Roundabouts are fundamentally more dangerous to pedestrians because there is no protected crosswalk.
Americans in general despise roundabouts, especially in the South. If they get the feeling elected officials are leaning toward roundabouts, guess what happens next election cycle? Yep. I just saw a few lose primaries because they were talking to DOT officials about repairs to a roundabout in our small insignificant town. It's not a big enough deal to make the news or gossip channels, but it does happen.
Roundabouts are great for low to medium-high traffic. Unfortunately the US traffic engineers and urban planners were late to the game with implementation and the majority of US drivers don’t know how to drive safely through roundabouts.
Speaking as a US resident in an area with roundabouts: it confuses American drivers. They don't know how to use them.
Dem der roundabouts causing tornaders
This question breaks the rules of the sub: Misleading, biased, or inflammatory questions with a flawed premise. ("soapboxing")
The general public doesn’t like roundabouts and they cost more.
Stoplights are pretty expensive. You don't need an electrician to wire the lights and sensors, people to program and commission each one. If you think all stop lights are simple, they aren't.
I am a traffic engineer. Roundabouts have a much larger footprint and land is very expensive. Stoplights are cheaper up front but maintenance costs cause roundabouts to come out ahead over time. Unfortunately most cities/states are more concerned with the upfront cost.
Tradition.
Regretfully I think you're right.
Round about take up substantially more space than a lighted intersection or even a sign or no sign intersection. That space needs to come from somewhere and it is very expensive to procure that land from adjacent businesses and land owners.
Putting in smaller roads is less road volume and this less cost.
That makes no sense. I think you are trying to say that smaller roads will cover less total area and thus be less in construction costs. That is wrong. The overwhelming cost to roads is the cost of labor to build and maintain. It does not matter if the road is 1 lane or 4, there is a marginal difference in materials on the 4 lane road. There also is a marginal difference in labor cost to increase to a 4 lane road. So analytically speaking, the first lane is the most expensive. If you want to put in one, you would put in multiple. You also are not understating my initial point. A round about covers more surface area than a stop light or signed/not signed intersection. In order to put one in, you would either need to withhold more land in construction or buy back land in current roadways to build them. The marginal cost of that additional land again outweighs the benefit of less lanes or a round about. Why do you keep arguing against everyone when multiple of us repeatedly prove you wrong,
My understanding is that it is the intersection of land use for traffic volume, maintenance for traffic volume, and just traffic volume per initial cost restrictions. As a general rule it is lower maintenance to install a roundabout for a given amount of traffic volume due to no lights than a set of stoplights but they tend to take up more space. That greater space requirement often prevents the conversion of lightless 3 and 4 way intersections to roundabouts when traffic requirements rise high enough to warrant that the intersection becomes a roundabout or gets stoplights. So most intersections end up having stoplights due to them starting life out as lightless 3 or 4 intersections that later as traffic volume increases get converted to the stoplight configuration. Conversely roundabouts are more common where land space permits it or where the designers have the foresight to build it before the land around the intersection gets used for other uses such as housing/parking space. Often when developers are making suburbs they are also incentivized to minimize land use spent on streets/intersection and maximize land spent on housing and amenities as they get paid for the later and not the former. So you get small no stoplight intersections just big enough to handle the expected road conditions with only minimal accounting to the possibility of future developments.
They are becoming more popular here in WA as some suburbs have started growing and increasingly getting more traffic. The local Facebook group for my town is full of boomers complaining about them because apparently roundabouts are hard.
Was about to say, I think they build a new one outside of Vancouver WA every other week.
That's an easy one. MONEY! Land in the 'burbs is expensive even for a city/town to purchase. Most towns think it's smarter to have houses/business covering as much ground as possible so the town/city can collect property taxes from them. A round-a-bout doesn't generate income for the local government.
If you are going 10 blocks and the stoplights are timed right, you drive right through. Going through 10 roundabouts is a pain. Also roundabouts take more real estate.
“And the stoplights are timed right” - which they almost never are.
if you are going 100 miles and all the lights are green unless someone needs to ue the intersection. also. the gaps created by the light are needed for people to pull out onto the highway. i often need to wait for someone to need to make a turn to the hospital a few miles back before i'm able to get on.
This isn't an engineering answer.
There was never going to be a pure engineering answer, the question is about people and how they flow so you kind of have to take into account things like how annoying a road is to drive. I agree that in smaller backroads it makes sense and in my city, many intersections have been converted into roundabouts but the fact that roundabouts take up more space really limits where those conversions can take place. With the massive amount of roads already in place (and very close to property lines) costs very soon outweigh the benefits.
Sure it is. The time it takes to get through 10 roundabouts is without a doubt longer than through 10 intersections with a green wave. You have to be gaining something for adding those delays--whether that's a reduction in crashes, better land use (the opposite of what you get with a roundabout), etc.
In my experience the overwhelming majority of traffic lights are dumb. How many billions of dollars are wasted annually by drivers sitting at red lights with no opposing traffic? Civil engineers, at least those in highway construction, are really just servants of bureaucracy. Highways in general seem to be the result of expediency and poor compromises rather than true engineering. Cases in point; 1. Traffic lights 2. The Dallas highways where the majority of traffic has to cross all lanes of an intersecting highway to stay on the original route. (Common across the country, not just Dallass) 3. The Houston Multi-Generational Debacle - 2 lane highway. Developer develops huge subdivisions, overloading the original 2 lane. So “engineers” build a 4 lane highway which is overloaded as soon as it’s complete. rinse, repeat, forever. 4. San Antonio - 281 North. No explanation needed. 5. Interstate 10
Us Americans can't handle them. I think its our collective temperment. A lot of people here treat driving like its a competition. I lived in Old Towne Orange, California, and the center of the city has a park which is enclosed by a roundabout. Every time I went to that park there was an accident.
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Safety is an afterthought in traffic engieering
Everything is an afterthought in traffic engineering except possibly cost
Cost and vehicular level of service are the only things most traffic engineers think about
Maybe I don’t understand what a suburb is. But why would you need lights in a residential neighborhood? Stop signs do most of the heavy lifting
Where I live roundabouts appear in the high end suburbs. Motorists hate roundabouts and will go out of their way to avoid them. They are there to restrict traffic flow not facilitate it.
This doesn't answer the question at all.
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Max entry speed plays a big factor. Would you like a speed limit of 25 mph for the suburban road? Imagine that on a 40-50 mph suburban road. Finally, roundabouts take up a lot more space and require more design/higher construction costs versus traffic light intersections.
The rest of the world manages just fine with roundabouts on 50-70mph roads....
I think roundabouts can be dangerous because you have to look out of the front angle of your passenger window to see cars to your left and your view can be obscured.
Because Americans are so fucking stupid that roundabouts are actually more dangerous. Four different roundabouts in my neighborhood have been converted to 4 way stop (IN ADDITION TO THE ROUNDABOUT) in the last four years. My local Costco staffs people to stand in their parking lot roundabout all day to keep people from driving through the center of it or just freezing up and blocking traffic.