How Many Roundabouts Is Too Many Roundabouts

Episode Transcript

Mollie (Host)
Welcome back to {Brief}ly Speaking, the SEH podcast where we keep things short, sharp, and focused on what matters most in the AEC industry. I'm Mollie, your host. Today we're exploring a question that can spark some debate in traffic design circles. How many roundabouts is too many roundabouts? Roundabouts are becoming more popular in the US, but they've been common overseas for decades, and the benefits and challenges are worth discussing. To help us navigate this, we're joined by Bill Klingbeil, who brings extensive experience designing transportation facilities, including roundabouts and arterial improvements. Over the past 20 years, Bill has been involved with more than 1,000 roundabouts. Yes, 1,000 roundabouts. And his approach to roundabout design blends careful geometry, signage, lighting, landscaping, and pavement markings to shape driver behavior and improve safety. So Bill, welcome to {Brief}ly Speaking.

Bill (Guest)
Thanks for having me.

Mollie (Host)
All right, to start us off, I just have to ask, I talked about it in my intro, but why are roundabouts so much more common overseas than they are in the US?

Bill (Guest)
I can tell you the brief history of roundabouts to answer this question. So we actually started with a circular intersection in the United States. The old rotaries that you'd see out in the Northeast of New York, New Jersey, those had different rules. They're a lot larger, speeds were higher. The rules for them were different. The people entering the roundabout had the right of way and the people circulating had a yield form. As cars became more popular and more traffic on the road, they would short circuit where so many people coming into the roundabout at one time, the circulating lane would back up and short circuit it. They then started using what they called semaphores, which are like traffic signals today to meter the entries and exits. So when they got to that point, with the speeds being high and the volumes being high and the short circuiting of it not being able to move traffic, they decided to go to signals where in Europe, they took that circular intersection and changed the rules. They decreased the size of it. They changed the rules where you yield at the entry and not inside the circle. So it always cleared that way. It made it slower, safer, and they wouldn't short circuit. and they could handle more volumes. They kept with that technology, changed it, improved it and used it. And then we brought it back over here around the 1990s, constructing in the United States.

Mollie (Host)
So we just pivoted away from it for a while there. All right. Well, good. That just, you know, talking about roundabouts, that was kind of the first question that popped into my head. I went over to Ireland a few years ago and there was a million roundabouts and I don't see that here. So now that we got that out of the way, What are the key benefits of incorporating roundabouts into street design?

Bill (Guest)
The main benefit is safety. The first roundabouts we put in the country were predominantly for rural high-speed intersections with fatal crash problems. They eliminate the right angle crash by reducing the speeds and creating a shallow angle of impact, getting rid of that T-bone crash. And so it's predominantly a safety benefit.

Mollie (Host)
Obviously you can't throw a roundabout at every single intersection. How do you determine if a roundabout is the right solution for a particular intersection?

Bill (Guest)
We typically go through what we call an intersection control evaluation or ICE as it's termed in the business. You start with defining the problem statement. What types of crashes are there? What's the frequency, the crash distribution, like what, you know, are they right angles or rear ends or sideswipes run off the road? And then what are the options we have for solutions to solve that? So it's not, you don't start with a roundabout and figure out, can we do something else? That's really what's the right solution. So depending on the type of crash, a roundabout can, like I said, solve the right angle crashes and those severe and fatal crashes. If those aren't the ones you're trying to solve, you may use something else. So once we start with the ICE, That kind of tells us with our traffic, our crash analysis of what we're trying to accomplish. You also look at traffic volumes, both existing and forecasted volumes, and to see how many lanes are you going to need, what is the configuration of whatever you're doing going to look like, and do you have the space to do it?

Mollie (Host)
So you talk about traffic volumes, pedestrian activity, that kind of thing. How do those influence, if you decide to make a roundabout, you say this one has a lot of accidents? We need one here. How do those influence the decision to design and install a roundabout?

Bill (Guest)
The pedestrian and traffic volumes will dictate the number of lanes you'll need. So you analyze for today's volumes that you measure, you look at the forecasted volumes as time goes and volumes grow. And then if you go from a single lane to multi-lanes, you do a sensitivity analysis in between to see when is that extra lane needed. So we try and build the simplest version first with the fewest conflict points. So the bigger and more complicated you make the intersection, the more confusing it is, the more crashes you could have. So we try and build the simplest thing first, but we like it to last at least 10 years, if not more. Then we try and make it easy to add on in the future. So it's not a major project, but just a small capacity improvement that could be done quickly and most of the roundabouts already in place. So it's kind of, it determines what initially gets built. It determines what type of phased implementation there may be and what the final product would be once the volumes get to where they believe they are. Pedestrians, trucks, bikes, those are all inputs as well. So I mean, if you have high truck volumes, those usually, increase the delay or you might need to build those extra lanes sooner than later if you have a really high truck percentage. If you have high pedestrian volumes that may increase like the crosswalk width, it may increase the delay at the intersection if you have that many peds. You may do things like signalization of the ped crossings to help with those movements at really high pedestrian volumes, like over 100 peds an hour.

Mollie (Host)
So you've done over 1000 roundabouts. Have you ever had a situation where a community was dead set on putting a roundabout, but either due to the ICE analysis or your just own personal knowledge, you didn't feel that it was appropriate?

Bill (Guest)
That comes up quite often, actually. They're kind of sometimes considered a silver bullet. If you have a problem, just put a roundabout in. So it really gets down to that intersection control evaluation and that defining what the problem statement is, your goals and objectives, going through the technical analysis and really being transparent in that process to show why you would or would not do it. A lot of times, there's other factors like amount of space you have and right away considerations, things that are kind of outside of just trying to solve capacity or safety problem that kind of constrain you and being able to do it. But there's also other technical things that come up that until you get into the granular details, for instance, unbalanced lane use. So you have 90% of the cars going on a main line, 10% going on the side street. A lot of times that'll create more delay at the intersection than what a signal would. But if you're trying to solve a safety problem, that might be a trade-off you're willing to make. Others that you might not see is a lack of turning movements. If everything is just two streets with through movements, roundabouts don't always work well. I've come across where signals will work better in those situations because you don't have the circulating traffic creating gaps. They really work efficiently with those turning movements that creates gaps for everyone and turns for them to go. So there's just a couple of things that have come up. And the pedestrian issue is always one where you have really, really high volumes. A lot of times they'd rather do a signal and pedestrian signalization at the intersection instead. And so those are common occurrences where roundabouts aren't always favored.

Related Content: Roundabouts 101: Basic Design Principles for Improved Intersection Safety

Mollie (Host)
I guess I never really would have thought of If it's just mostly straight traffic, that makes sense that a roundabout isn't really necessary there. And I kind of feel like a roundabout is becoming the more trendy thing to do. Are you seeing that at all?

Bill (Guest)
Well, they're more popular. I mean, signals aren't safety devices. So if safety is paramount and you're willing to trade things off for safety, consider a roundabout. And a lot's changed in the 20 years, early on in the career when I was doing these. you had private businesses that say, you'll put me out of business if you put a roundabout in. And I'm like, help me understand why. And they're like, well, they're going to get through so efficiently, they won't see my sign and come by, stop at my store. Trucks are like, oh, you can't put a roundabout in because I'll get in a crash and lose my license. And then later on, we're at by truck intermodal stations where you're going from rail to truck transport and they're asking for roundabouts so trucks don't have to stop because coming to a complete stop for a truck, burns a lot of gas. So they like the efficiency of the roundabouts. But it took years, decades to get there. And even private businesses now ask for them because you put them in series, you can do access management, make it easier to get to their business than, you know, someone can't make a left turnout. They'll never come back because it's just too big of a pain to get out of the leave once they get to their business. So sometimes with being able to turn around and do the U-turns with roundabouts, business will ask for them. So I've been in those cases too. And that wasn't the way it was early on. So it's nice to see it become a little easier now. And even with pedestrian crossings, those used to be a deal breaker 20 years ago with these. And now, you know, my home state of Minnesota, they did a, MnDOT did a study on pedestrian crossings and all the roundabouts in the state. And I think Minnesota's 8th in the country in number of roundabouts and most of them are on arterial and collector roads. So they're not in developments. And so they studied the pedestrian crashes at them and there's tracking with the same safety benefits as the vehicles have with like a 90% reduction in fatalities, a 70% reduction in injury crashes and a 40% or so reduction in overall crashes. So, you know, we didn't have those types of studies early on to try and sell the roundabouts or build the trust in the public that they're a solution. So those are some things that have changed over time that are making them a little easier to implement. Also, from a cost perspective, doing signals are getting more expensive. You look at a 24-hour delay instead of just a peak hour delay. You know, you don't want to sit at a signal for a minute and a half at night when no one's around. Roundabout, you just slow and go. So there's other factors you look at when you compare what are your goals, you know, that make roundabouts more appealing.

Mollie (Host)
I'm sure there's a maintenance factor there too. comparing signals to just a roundabout. All right, I'm gonna throw an example at you. So if I'm a community with a notoriously difficult intersection, but just down the road, there are already back-to-back roundabouts. Should I put a roundabout at that intersection or is that too much?

Bill (Guest)
You have to look at the entire corridor. So a couple things to know about when you're looking at a corridor system transportation system. If you already have a couple of roundabouts and you put roundabouts in series, when you have all roundabouts, they work really well together because their gaps are more random, where signals, you have big platoons. So you have really long platoons, but then you have long gaps, roundabouts, you don't have platoons, but you have more gaps, but they're just more random. So when you have them in series, they work really well with random arrivals and departures. You put a signal next to a roundabout, you have a big platoon come into the roundabout, and then they can't, it just can't process all the traffic really fast. It takes time. So it doesn't work as efficiently. You know, another thing to to consider is the side streets between the roundabouts or the nodes, whether it's a signal or roundabout. Trying to get side street access on minor roads between the major intersections where roundabouts would be at is a little more challenging with a series of roundabouts than with signals, because with signals, you have those really long periods of gaps that you know you're going to wait a little while, you're going to get that really long period if you can time your signals right. where you get that left turn out. So there's a couple things to trade off there, but with the roundabouts you get the U-turn capability. And so you really have to look at the spacing, the number of them. If you have signals in between the roundabouts, that inefficiency is going to look like. It might not work as efficiently as you think if you throw a signal in between the roundabouts and the signals won't work as efficiently if you throw a roundabout between all the signals. So you really have to look at it from a whole system and model it and understand the trade-offs.

Mollie (Host)
And essentially what your goals are, right? You talked about is it more of safety? Is it traffic flow? Is it pedestrian safety? So it makes sense that you'd have to look at the whole picture.

Bill (Guest)
Yeah, in this case with a really bad intersection, if it was uncontrolled and you had a high volume of traffic trying to get access and you had roundabouts nearby, putting a roundabout there would probably work well because it's kind of working with what the system has on it already.

Mollie (Host)
So we briefly touched on maintenance there. I kind of want to go back and talk on some more design considerations, that kind of thing. So how do roundabouts impact construction costs, right-of-way needs, and then maintenance compared to traditional intersection?

Bill (Guest)
Construction costs, roundabouts oftentimes are a little bit more on the initial construction costs, but less in the life-cycle. Overall, with a signal, you're always there maintaining it, eventually you have to change the arms and the heads, redo the timing and reach change light bulbs if someone hits the pole or not. Roundabouts, it's, you know, the initial cost may be a little more and depending on what the right-of-way is like, typically the right-of-way is the killer. If they have corners out to the intersection, it's in there, you're putting a big circle in there, it'll cost you for a right-of-way. So that could be a larger initial cost as well. Maintenance, as I mentioned, there's the comparison between the signal and the roundabout, but there's also the snow removal and things like that are often discussed. And I think we've really overcome those types of maintenance issues for folks that have winters. And then there's the pavement maintenance where we're doing more roundabouts and concrete because that concrete over time, a lot of times you'll have to close an intersection down for a roundabout if it's a single lane. to do pavement maintenance. If it was asphalt, you mill and overlay at concrete, you do joint repair. So we look at the pavement maintenance and what type of roundabout you're doing in that calculation as well to make sure, you know, we're comparing apples to apples when doing that comparison. Then constructability is another thing with a signal. A lot of times you can just shift traffic over one way or another and kind of checkerboard your way into constructing the intersection to keep it open. Roundabouts a lot of time, you'll do bypass alignments or full closures and kind of a comparison between how do you want to rip the band-aid off? Do you want to pull it really slowly or do you just want to rip it off? So you do a bypass alignment that takes extra time, extra cost. It can keep maintain traffic or you just do a full closure and and throw some incentives for the contractor, get it done in a short period of time, and it can get in and out quick. The more you build on a roundabout, the bigger chunk you can build on the intersection, the better product you get. So that's kind of the goal when analyzing the constructability or construction of it. And that's where the bypass lines come in because it allows you to build more of the roundabout at one time with maybe only shutting one movement of the intersection down and minimizing detours, but it comes with a cost.

Related Content: Exploring the Circular Logic of Roundabouts

Mollie (Host)
What are the design limitations of a roundabout? How many lanes are we talking?

Bill (Guest)
The largest roundabouts in the country, there's a few of them now and it's hard to keep up with them because they're coming so fast. In Michigan, they have some with three lanes entering and circulating. You start getting to those volumes, you're almost looking at a grade separation, some type of interchange that would really be a better solution than trying to do a three lane roundabout, three lanes in each direction. the most common type will be maybe two lanes in each direction for a multi-lane roundabout and maybe you'll have a third lane that's just a right only. So those types of volumes and it depends on the, I can't throw a number out because it depends on how the volume distribution around the intersection and the turning movements to see how much that is. But when you get into design, that's about how many lanes you see. And it has to be kind of an extenuating circumstance when you get to three lanes everywhere, like there's nothing else you can do. It's the best of a bad situation maybe.

Mollie (Host)
Yeah, that feels that feels a little intimidating. Talk to me about how signage, lighting, landscaping, and markings, how do those play into roundabout communication, design, all of that.

Bill (Guest)
Sure. Roundabout is a system. it's all those components you just mentioned, the geometric design, the vertical design, the signing, striping, landscaping. If you can't do everything perfectly, some things you enhance to manage the trade-off you can't do somewhere else. So, you know, the most powerful attributes of a roundabout that communicate to the driver are the geometrics. And so you try and get those right. You know, sometimes the spaces that are available to be perfect. So then you can implement the landscaping. So geometric design gives you the visual cue coming in, the curvature to slow you down, but there's the landscaping that really makes that central island visible to the drivers as a strong visual cue. It keeps the headlight sight from going through. But you also have it on the approaches as well that can help the corridor feel narrower. So on high speed approaches, you get them to slow down a little more. You have to be careful with it so you're not hiding pedestrians at intersections and things. So there's an art and a science behind it. And then, you got to keep the center island free of obstacles. Medical emergency, drunk driver, someone like distracted, whatever ends up going through the middle. You don't want an obstacle there to injure anyone. So that's kind of the landscaping component. The signing, you know, we try and carefully place it, minimize the amount we need because you can only take in so much information at once. But giving the drivers the information they need at the time they need it to make a decision, it's really critical on the multi-lane design. So we try and get them in the correct lane before they get to the intersection. So that's important. And it gets down to the details of what's different between a roundabout and a standard intersection. So there's little details I've dealt with on plans. And I mean, I used to, I still do sometimes go from concept all the way through construction being involved with the project because you get the for instance, the placing of a yield sign. And a lot of times you look in the book, it says perpendicular to the curb, and that's where the contractor will install it. Well, roundabouts have a bunch of curves coming into them, and now you can't even see the yield sign because it's not perpendicular to the eyesight of the person approaching. It's perpendicular to the curb, but now you just see the edge of it. So those little details like that, you really need to be cognizant of in the design. So the signage will give you the input you need to make a decision at the approach. The striping really helps reinforce those lane assignments. And that's something we're still working on in the industry on the multi-lane roundabouts, the striping on those. All those parts and pieces put together is really how the roundabout works, even with the pedestrian crossing locations, you know, for the driver to address the pedestrian before the yield line so they're not looking to their left. They're focusing on the pedestrian to make that a safer environment for them as well.

Mollie (Host)
No, that leads perfectly into my next question. We've talked a lot about there's driver safety and then there's the pedestrian factor. Is that more of a trade-off, so to speak, or are there ways to design roundabouts to enhance pedestrian and cyclist safety?

Bill (Guest)
So this is something that's been going on for as long as I've been doing this. The biggest pedestrian issue with roundabouts, two of them, the multi-lane roundabouts with one on the approach or exit, if someone yields on one lane and a ped's crossing, the second lane doesn't know why the first car stopped, they may keep going. So that's the fear. And then you throw in visually impaired pedestrians that can't see if a car is stopping or not. And that's been the biggest challenge with multi-lane roundabouts since early 2000's or since we've been doing them. So there's been a few, ProWag just came out with an update last year. If you're doing a multi-lane roundabout, they'll want a raised crosswalk or some type of signalization or RRFBs, rectangular rapid flashing beacons, or hawk signals, other types of pedestrians signalization. to compensate for those multi-lane roundabouts. So the raised crosswalks, they force folks to slow down more. And on the exits, there's a trend that when you're on your accelerator leaving the roundabout that you're less likely to yield for pedestrians at the exits. So those raised crosswalks really force people to slow down and get their feet off the gas pedals and more likely to yield for the pedestrians. So those are, that's a, I mean, that's a new thing in the industry for multi-lane roundabouts. but the pedestrian safety part of it, like I said earlier, those, study out now, there at least there's one in the country that does show that they are safer for pedestrians, especially the single lane roundabouts. And the pro-ag folks left the single lane ones alone and really targeted the multi-lanes because that's where the perceived issues were at with the roundabouts. So I would say it's a perceived issue in some cases. I usually at public meetings when someone asks, like, how am I supposed to cross? How are you supposed to cross the street at a roundabout? And I usually ask, have you ever crossed one? And a lot of times they'll say no. It's like, well, it's not that hard if you've actually done it. You only have to look at traffic from one direction and make a decision. So for instance, they put roundabouts at schools A lot. I don't know if I'm going too far into the weeds here, but they have a program out in Avon, Colorado where they did at least years ago where they called it PEDS, point eye contact decide. They teach the kids at school that you hold your arm out in front of you, kind of like pointing where you're going to walk when you're at the crosswalk. You make eye contact with the driver and you decide if they yielded for you or not. And so they teach the kids this in school, the kids could teach their parents. I mean, it's something that, you know, even when they were doing the experiments with roundabouts and driver behavior and yielding compliance, Once they had people that would signal their intent to cross the road, they had the compliance went up in the 90 percentile range just because cars then knew what the pedestrian is going to do.

Related Content: Creating Safer Streets with a Pedestrian Crossing Policy

Mollie (Host)
Just inherently, when you think about there's not that red light stop pause time section for people to cross, it would cause concerns. But when you bring up the point of saying you only have to look one direction, if there's a break in it, then you're good to go. That makes a lot of sense.

Bill (Guest)
You have a two stage crossing, right? You have a median you yield in. So you're only crossing one or two lanes at a time, but not four or six if you have left turn lanes and right turn lanes and four lanes. And so you have fewer lanes to cross and you get a break in the middle, a refuge, and then you look from the other direction. So it simplifies it, but it still puts the onus a little bit on the pedestrian. But at a regular signal, would you ever cross just because you saw the cross sign and not even look if a car was complying or not. we always really look to see if someone's really stopping or not, or at least we should be.

Mollie (Host)
We've talked through why and how to use roundabouts. We covered that. If a community is listening and they're now considering adding a roundabout to one of their streets, what's their first step?

Bill (Guest)
Identifying the problem that they're trying to solve with the roundabout. If you're going to sell a community on a roundabout being a solution. You have to be transparent in why you're doing it. So, and I really hammer on that working with communities, different agencies or who's ever trying to implement one is like it's a solution to a problem. So let's really identify that and what we're trying to solve. And then it's, you know, we're identifying the problem we're solving and we're going to be transparent on also the benefits you get from using a roundabout for it. And then there's the education part of it with, you know, how to drive them and how to use them, that follows on as well?

Mollie (Host)
So is there like a specific trigger for the technical ICE analysis or is that just a normal part of the process?

Bill (Guest)
That's usually happens at the front end of the project when you're looking at we have a problem at this intersection, what should we do? That's the ICE where the ICE comes in and does all that analysis.

Mollie (Host)
Are there resources or tools that communities can use to either evaluate potential locations or find funding?

Bill (Guest)
Yeah, agencies, you know, I'll give a tip of the cap to a lot of cities and counties and the DOTs out there. They're pretty savvy on the funding part, typically, especially the metro areas are always doing it. A lot of metro communities, you know, have folks on staff that are always doing the funding applications. I know at SEH we help a lot of communities out and a lot of agencies, DOTs, counties out with the funding applications as well. So it's really looking at those high crash or high delay or where the complaints are coming from the folks because not everything shows up in a crash report. A lot of times they get complaints on the near misses and I'm waiting here a long time and that kind of triggers like, hey, let's go do counts or a delay study or something like that to help identify the problem.

Mollie (Host)
If you have a piece of advice to give to a community looking to start a roundabout, what would it be?

Bill (Guest)
Seek input, start with the questions. hire someone who's done this before that knows the questions to ask. You get the right input and you'll get a great product at the end of the day. So it's really asking those questions, engaging the stakeholders that'll use it, the community. What is it that they need? What are the details, the types of vehicles that go through? Are there farm implements? Are there oversized vehicles, low boys? That type of detail that you put into it to get a design that accommodates all of it. I tell the communities I work with, it's like when they question if vehicles can get through it or not, I go, you tell me what vehicle goes through this and I'll make sure it gets through. I mean, we'll figure out ways to do it. So it's really if community's looking at some- it doesn't matter if it's a small town or a big city, it's that input you get into the project, into the design from the community, from the stakeholders, businesses, everyone that makes it a successful project. And that's what I spend a lot of my time doing with communities is really upfront getting that input in to create the design.

Mollie (Host)
All right. Well, thank you, Bill, for going through all of this roundabouts, giving us some of those details like you just talked about. It's clear roundabouts can be safe and sustainable, but like anything in design, balance is key. That is all for this episode of {Brief}ly Speaking. Be sure to follow us for more short, sharp conversations on what is shaping the AEC world.