2005 August 06
Last update: 2009 Oct 19. See History for brief descriptions of changes and updates.
This post is written for those who are interested in an introduction to Roundabouts, and don't wish to read the longer post concerning a specific proposal for Old 27 North and Livingston Blvd in Gaylord, Michigan. Included are references to applications, design considerations, public acceptance, safety, pedestrian accommodations and safety, and before-and-after examples. Many of the same links to the internet are used, but are organized in a different sequence.
This post is essentially complete, but may be updated for new information concerning roundabouts in Michigan. The links have been checked, but some are changed by webmasters from time to time. Add your comments and questions so that the post can be continuously improved. Thanks.
Don Nordeen
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Read the continuation of this Post and any Comments.
Or Click Show All for the Above Introduction and the Continuation of this Post and any Comments.
Introduction to Roundabouts (continued)
Memo on the Internet Links
This post makes extensive use of information on the internet.
- To review the internet references, click on the highlighted words for internet page or download. All of the websites have their own links, so you can explore many of them as much as you desire.
- To return to this post, click on your browser's back button/arrow (may require multiple clicks depending on how much you explored).
- If your browser has a "snapback" feature, mark this post for snapback. Then click your "page snapback" to return to this post.
Introduction
Handling traffic at intersections has been studied almost since the beginning of the automobile. Police directing traffic was an initial solution. Stop signs. And then traffic lights. For major highways, the USA adopted the over/underpass as the preferred solution. The interstate highways all used this method with cloverleafs and other schemes for handing ingress and egress from the interstates.
Traffic circles were also introduced in a few areas of the country, but with limited success. The circles were of relatively large diameter to allow for merging at higher speeds. For many reasons, the use of traffic circles was limited, and the hoped-for benefits in traffic flow and safety didn't materialize.
Europe, and primarily the UK, pursued improvements to the traffic circle with significant changes including the use of the name, roundabouts — typically British. The roundabouts had/have different features:
- smaller diameter circulating roadways with lower speeds for merging, ingress and egress
- lane splitters to funnel the traffic into and away from the circulating roadway
- pedestrian crossings away for the circulating roadway with center "islands" so that pedestrians need to cross only one direction of traffic at a time
The contrast between traffic circles and roundabouts is graphically shown the before and during conversion of a traffic circle to a roundabout in Kingston, New York. After accessing the site, move your mouse pointer across the picture to see the "before" and
"during construction" layouts. Two different "after" pictures are
available in the second picture, again my moving your mouse pointer over
the picture. Scroll down to more information. Access this information at Kingston [URL is http://www.alaskaroundabouts.com/mythfact1.html.].
More before/after pictures are available at Alaska Roundabouts. The text at the web page provides the explanation of the changes including before/after
for the Kingston roundabout. Scroll down to the last picture of a
Bruhl, Germany, conversion of an urban intersection to a roundabout.
Move your mouse pointer over the photo to see the change. Note that
the roundabout uses same real estate (actually less with the added "plaza" area in the lower left) as the
intersection. Also note the more attractive appearance: no tall
poles, no traffic lights and wires, landscaping, and center island safe
zones for pedestrians. Also note that this website contains a wealth of information as shown in the left column. Access this information at Project Overviews [URL is http://www.alaskaroundabouts.com/case.html.].
Your Driving Experiences — Have you ever stopped at a traffic light and waited patiently for the light to turn green even though there is no other car in sight? Of course. This won't happen with a roundabout. It automatically (passively) adapts to the traffic flow. If there is no traffic in the circulating roadway, you proceed directly through the roundabout and exiting right, through or left as you desire.
To see how the roundabout works for drivers pedestrians and bicyclists, look at one or more of four internet demonstrations provided by cities that have roundabouts.
- The demonstration for the Clive, Iowa, Roundabout was created as part of the education while the roundabout was under construction. In my view, it is the best demonstration on the internet. The graphics also illustrate the adaptability to various road types (divided four-lane road left and right; divided two-lane road at the top; undivided two-lane road at the bottom) and features of a well-designed roundabout: lane splitters to direct the vehicles into and away from the circulating roadway; two-lane circulating roadway; pedestrian crossings back from the circulating roadway with center 'safe zones'; land use essentially the same as for a traffic-light controlled intersection with separate turn lanes and sidewalks; and the landscaping. Click on Clive [URL is http://www.cityofclive.com/departments/public-works/traffic/Roundabouts.php.], then click on “demonstration” and follow the instructions to interact with the demonstration.
- The second is in Sammamish, Washington. Four different demonstrations can be accessed by scrolling to the bottom of the page. Select demonstrations for left, through and right turns. Finally, check out the roundabout safety. To see this demonstration. click on Sammamish [URL is http://www.ci.sammamish.wa.us/RoundaboutDemo.aspx?Show=Main.].
- The third demonstration has been provided by Jefferson County, Colorado. In the paragraph, "How do they work?" click on "interactive
demonstration" and be careful not to honk your horn. When you are
finished honking your horn, click on "Play without Rules" to view random traffic flow without interruption. To see this demonstration. click on Jefferson County [URL is http://www.co.jefferson.co.us/highways/highways_T48_R17.htm.]. Scroll down to "How do they work?" and then click on "interactive demonstration" for the demonstration.
- A somewhat different demonstration is available from Waterloo, Ontario. Follow instructions and click on what demonstrations you want to observe. To see this demonstration. click on Waterloo.
As illustrated in the demonstrations, the rules are straight forward: yield to vehicles in the circulating roadway, yield when changing lanes and yield to pedestrians in the pedestrian walkways.
Vehicle and Pedestrian Safety — Pedestrians first. The pedestrian walkways are located back away from the circulating roadway. Traffic is moving slower due to the geometry of the roundabout. Pedestrians cross only one direction of traffic at a time with a center island 'safe zone' before crossing the other direction of traffic. Vehicles yield to pedestrians.
Vehicle safety is fundamentally improved by the slower speeds. But other features help as well. The lane splitters are the entrances funnel the traffic into the circulating roadway where the traffic merges. The serious crashes are prevented: front into the side of another vehicle, front-to-front head-on crashes during left turns, and front-to-front head-on crashes. When crashes occur, they are glancing crashes at lower speeds.
Consider two recent crashes in the Gaylord area, one with a fatality (at M32 West) and a second with a serious injury (McCoy and Krys Roads). Both involved a vehicle waiting to make a left turn that was impacted in the rear and pushed into the oncoming traffic. The most serious part of these crashes was the "second" head-on crash, not the rear impact. Because of the geometry of the roundabout, the likelihood of the rear impact is reduced. But more important, if the rear impact does occur, the front vehicle will not be pushed into oncoming traffic creating a more serious head-on crash.
Memo: One of the driving tips is to keep your front wheels pointed straight ahead when you are waiting to make a left turn. Then, if you are impacted in the rear, your vehicle is less likely to be pushed into oncoming traffic. Unfortunately, we are usually in a hurry and turn the steering wheel to the left while waiting for the traffic to clear.
Michigan Roundabouts
Michigan Department of Transportation — (updated 2007 Nov 03) MDOT provides general information about roundabouts at What is a roundabout? A quotation, " Modern roundabouts are superior to old-style traffic circles and to conventional intersections at many locations." The photograph shown is of the M–81 roundabout at I–75 in Saginaw described further below. MDOT provides links to other internet documents regarding safety and other factors. Click on "several roundabouts" in the first paragraph for some locations of completed roundabouts in Michigan. Click on "online demonstration" for an animated demonstration of how to use a roundabout. A chart "Percent reduction in traffic delays and stopped vehicles after roundabouts constructed" shows the improvements roundabouts provide. Included are links to other internet sites that provide additional information. Some of those links are included in the references at the end of this paper.
Okemos — In part because of the excellent graphics, this roundabout is featured in the literature and appear in many places on the internet with favorable reviews. The roundabout is located at Hamilton (2 lanes undivided to the east and 4 lanes undivided to the west) and Marsh Roads (2 lanes undivided to the NNE) in Okemos, just south of the Meijer’s Store. The combination of different types of roads connected to the roundabout illustrates the flexibility of the roundabout concept. This website provides links to basic information about roundabouts. This roundabout is described at Okemos Roundabout [URL is http://www.roundaboutsusa.com/other_us.html.].
Brighton — This is a conversion of a downtown intersection to the Brighton Roundabout [URL is http://www.detnews.com/2003/livingston/0307/04/c05l-207920.htm.]. The Detroit News article provides background and reasons for selecting a roundabout. (added 2006 Jun 1) Sorry, the Detroit News article is no longer available on line.
Dimondale — This mini-roundabout in Dimondale (just SW of Lansing) has also been featured in the literature for its simplicity and low
cost. The little
island in the front of the pricture is the lane splitter. Behind that
is a small raised circle with the circular arrows. It really is a mini-roundabout
(small center circular island with climbing ramp for trucks and
busses). The cost of construction was very small. It has been
specifically designed to use the existing right of way. See this
mini-roundabout at Dimondale [URL is http://www.roundaboutsusa.com/minis.html.] and then click on the "Mini-Roundabout Michigan" picture. A 2005 technical paper, The Dimondale Mini: America’s First Mini-Roundabout, [URL is <http://www.teachamerica.com/roundabouts/RA054A_Waddell_ppr.pdf>.] provides comprehensive information about the location, design and results for this mini-roundabout.
18 1/2 Mile Road and Van Dyke in Macomb County — (description revised 2007 Nov 03) This is a major intersection with high traffic volume. It is located in Sterling Heights, and is just south of Utica. Van Dyke is the major N-S street through Utica. This project illustrates the use of a roundabout to provide the interconnections for surface roads and with a limited access freeway. An aerial view below shows the area before construction of the roundabout. 
Click on the image to get a separate and larger view. The roundabout was constructed in the vicinity of the intersection of
18 1/2 Mile Road and Van Dyke Avenue. Northbound M-53 turns to the east from Van Dyke and
becomes the M-53 Freeway.
A Google hybrid map below shows the aerial view before construction with the road information as constructed. Click on the image to get a separate and larger view.
This hybrid map shows how the new roundabout connects to M–53, which is a surface street (Van Dyke Ave.) to the south and becomes a freeway to the northeast.
A multi-lane roundabout has been constructed. The arrangement is shown in the diagram below. Van Dyke Avenue is the N–S road with north at the top. The road to the west is 18 1/2 Mile Road. The road to the east is an exit road from southbound M–53 freeway. The loop at the bottom right is not part of a "cloverleaf" but rather is a connection to and from northbound M–53. Refer to the hybrid map which shows the M–53 transition from Van Dyke Avenue (to the south) to the M–53 freeway to the northeast.
Click on the image to get a separate and larger view. Note that
the roundabout accommodates three lanes each way north and south. Refer to the aerial photograph.
Interestingly, there are remote video cameras at this site. Below is a still shot taken from one of the video cameras directly to my computer.
Click on the image to provide a separate larger image.
This photo is taken looking west on 18 1/2 Mile Road. The traffic from the right is southbound Van Dyke (three lanes).
The picture was taken on Saturday, 2005 August 6 at 1337 (1:37 pm) — a time when the traffic volume is relative low. Note that the southbound traffic (entering from the right in the picture) is slightly queued waiting for the vehicle in the circulating roadway to complete its turn. Most of the time on this Saturday afternoon, there were no queues. And, of course, no traffic lights and no waiting, either.
Also note the pedestrian walkway with its island safe zone.
The picture below was taken on Monday, 2005 August 8 at 1738 (5:38PM at the height of the rush hour). It is essentially the same view except looking a little farther to the left (south).
Click on the image for a separate larger view. The picture was taken at a time when there were a number of vehicles in the circulating roadway. However, gaps in the traffic allow almost continuous traffic flow. Note the car entering from the right. The gap at the left allows the "oncoming" traffic to enter the roundabout. Even though there is a queue on eastbound 18 1/2 Mile Road at the top of the picture, the traffic was continuously moving, although at a slower speed than on Saturday afternoon when the traffic volume was lower.
Fifteen minutes later, there was no queue as shown in the picture below taken at 5:53PM.
Again, click on the image for a separate larger view.
Read more about this modern roundabout in the MDOT Article [URL is http://www.michigan.gov/mdot/0,1607,7-151-9620_11057-92838--M_2004_5,00.html.].
14 and 15 Mile Roads West of Orchard Lake Road in Oakland County — This set of projects is the granddaddy for roundabout construction in Michigan. A Detroit News article describes the construction of nine roundabouts on 14 and 15 Mile Roads between Orchard Lake and Haggerty Roads in Farmington Hills and West Bloomfield Township. A map showing the location is at the bottom of the article. A major highway, Northwestern Highway, dead ends into Orchard Lake Road near 14 Mile Road. The article also shows the layout of the roundabout at 14 Mile and Orchard Lake Roads which will also handle the traffic from Northwestern Highway. Read this article at Detroit News Article [URL is http://www.detnews.com/2002/metro/0205/09/a01-485304.htm.]. (added 2006 Jun 1) Sorry, the Detroit News article is no longer available on line. More information is available from the project consultants at DLZ [URL is http://www.dlz.com/seg/index.html.].
M-81 Interchange at I-75 in Saginaw, Michigan — (added 2006 May 27) An artist's rendering of these two roundabouts (looking west) on M-81 at the entrance/exit ramps for I-75 shows the location and layout. Note that much less land is required than for the traditional clover-leaf interchange. Also no traffic lights even though the entrance and exit traffic is high. Also note that the geometry of the roundabout makes it difficult to exit the roundabout the wrong way onto an exist ramp from I-75. The several lane splitters at the entrance/exit from the roundabout direct the traffic into the correct circulating or exiting lane. This information as of 2006 May 27 copied from the MDOT website is shown below.
M-81/I-75 Interchange Reconstruction:
What we are doingMDOT will be reconstructing the M-81/I-75 interchange. Work includes:
- Replacement of the M-81 bridge over I-75,
- Construction of two modern roundabouts at the interchange,
- Landscaping, lighting, drainage and safety improvements on M-81 between Outer Drive and Wolf Road in Buena Vista Township.
This will be the first roundabout of this type (having double roundabouts at the ramp terminals) in Michigan and it will greatly improve the operation and traffic flow of this interchange.
Time span:
April 2006- November 2006
(added 2007 Nov 03) This roundabout is now complete and was opened on 2006 Dec 06. See M-81/I-75 Roundabout To Open on Wednesday. Also see the Federal Highway Administration summary titled Michigan >Traffic Bottlenecks > Combating Bottlenecks for brief description and cost. A quotation summarizes the project, "At $5.1M this solution represented a cost savings of $6-7M over typical reconstruction. In essence, the "roundabout solution" has reduced delays, reduced fuel consumption (which has reduced air pollution emissions) and the LOS of C/D has improved to A with on [sic: no] visible traffic back-ups." The $5.1M cost includes replacement of the bridge over I–75 which was replaced because of its deteriorated condition.
US–23 & Lee Road near Brighton, Michigan — (added 2007 Nov 03) Also check the multiple roundabouts at the interchange on US–23 at Lee Road just south of Brighton. See Green Oak Village Place Roundabouts . The photograph shows the various lane splitters, islands and bypass lanes which funnel traffic into the correct lanes. The road markings are also clearly visible in the photograph Click on "Click Here for Virtual Information on Navigating the Roundabouts" for much more information.
Technical References
[1] Stephen G. Metzer, AICP, “Use of Modern Roundabouts for Congestion and Safety Improvements” DLZ Engineering, Columbus, Ohio, presented at the 2002 Ohio Transportation Engineering Conference on October 22. This is a collection of slides — an easy read with the graphics and
illustrations. Included are pictures of several roundabouts including a considerable
discussion on the Oakland County "granddaddy" project on 14 and 15 Mile
Roads in Farmington Hills and West Bloomfield Township. This presentation is available at Modern Roundabouts [URL is http://www.otecohio.org/otec%20presentations/tuesday3pm/Metzer-2002%20OTEC.pdf.].
[2] Richard M. Barnett, Jr., “Roundabouts and Traffic Circles,” ABNA Engineering, 2000 Dec 29. This is also a slide presentation of 84 slides with a first page index
linked to the appropriate slides. {Memo: I saved the browser file for
off-line viewing for faster switching from slide to slide.} The
graphics and illustrations are easy to read. Most of the pictures are
before and after construction of roundabouts. The presenation includes important
favorable information on safety and public acceptance. Available at Roundabouts [URL is http://www.abnaengineering.com/abna/.].
[3] Alaska Roundabouts has a wealth of information. The site is easy to navigate using the contents in
the left column. Good pictures and graphics. Some pages provide
explanations. There is even a webcam page to allow you to view places
around the world. For the webcam, click on "How to use a roundabout" and scroll to the bottom of the page. All of this and more are available at Alaska Roundabouts [URL is http://www.alaskaroundabouts.com/index.html.]
[4] RoundaboutsUSA also has a lot of information. Pictures of many roundabouts are available on the right side of the home page. In addition to the links at the top (Introduction, History, ...), there are links to many current articles toward the bottom of the home page. Just explore and have fun. Available at RoundaboutsUSA [URL is http://www.roundaboutsusa.com/index.html.].
[5] Pictures of Various Roundabouts. (added 2006 Jun 1) Pictures are available from City of Portland [URL is http://www.portlandonline.com/transportation/index.cfm?a=62488&c=35932.]. Review the pictures of various roundabouts. The pictures of the Okemos roundabout are near the bottom. As you scroll down, note the roundabout at University Place, Washington, which shows that roundabouts do not require more land than the conventional intersection. Most of the above websites also have pictures, search on the internet for "roundabouts."
[6] Papers and Articles by Insurance Institute for Highway Safety (added 2009 Oct 19) The IIHS website provides a layman's discussion of roundabouts in a series of papers and newsletters. The site includes a video showing how roundabouts work.
Memo: I may add other internet links to a few of the technical references available on the internet, but want to be selective for the non-technical reader. Most of the other sites are available as links from the various resources linked in this post.
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Copyright 2009 © Donald L. Nordeen. All Rights Reserved. See Copying Posts on This Weblog.
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2006 Aug 22
Why do you only show 18 1/2 Mile entering and exiting? What about the rest of the roundabout? Also, There's a good view of how it was but the "sketch" is wrong. It doesn't look anything like the actual roundabout. For one thing it shows N.B. Van Dyke looping around back towards 18 Mile. It doesn't do that at all. How do you get to N.B. M-53? S.B. M-53 spits after Utica Rd. One part goes to the Roundabout and the other goes up and over both N.B. Van Dyke paths and to 18 Mile. There's only a small section with 3 lanes, all the rest is 2 lanes. It doesn't show how to get from the roundabout to N.B. M-53.
====Reply====
2007 Nov 03
The explanation has been revised. However, no change was made in the sketch which is from DLZ, the traffic engineering company that designed the roundabout and connecting roads. DLZ has published more information on the internet with a sketch that has not been cropped and shows the loop connecting to southbound Van Dyke Avenue.
Posted by: Glenn S. Meunier | 2006.08.22 at 18:49