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HomeMy WebLinkAboutCOM 0496.009 2004-2006 •TV o. Phone No.: (808) 961-8026 r>i'•'~~ ~ Fax No.: (808) 961-8912 E-Mail: JWeatherford@co.hawaii.hi.us .+:•~r • h~0i N'+ HAWAII COUNTY COUNCIL County of Kawai 'i Hawaii County Building ~ Aupuni Slree/, Sure 209 ll7/u, Hawaii 96720 To: Hawaii County Council Members i From: James Weatherford, Ph.D.. Legislative Assistant Date: ,lanuary 9, 2006 Re: Information regarding roundabouts Attached arc five brief documents with information regarding roundabouts, including information on issues that have been raised by Council Members. These documents cover: • basics of what roundabouts are and how they work; • advantages and lirnitations of roundabouts as an intersection design; • common misconceptions about roundabouts; and • sources of further information about roundabouts. Should you have any questions. please call me. Comm. No, ~Ef. r~: W it~~, C c,t y r Alternate Traffic Control: Roundabouts , by Michael J. Wallwork, P.E., Genesis Group, Inc., Jacksonville, Florida Is there an alternate to traffic signals that has the safest form of conflicUintersection control, that has the lowest delay and can be landscaped? Roundabouts are all of these things and some information about them is below. Don't let other engineers send you around in circles! Advantages of Roundabouts Safety: roundabouts in the USA and other countries have achieved a 50 to 90 percent reduction in collisions compared to intersections using 2- or 4-way stop control or traffic signals. Pedestrian/vehicle and bicycle/vehicle collisions at roundabouts are rare. This reduction in crashes occurs for several reasons: • The number of possible conflict points between vehicles decreases from 32, at a 4-way intersection, to 8, at a roundabout. By reducing the number of conflict points the number of collisions is reduced. • Vehicle speeds at roundabouts are much lower, generally less than 40 kph. Lower speeds means shorter braking distances and longer decision making time. Therefore, even if someone makes a mistake, a collision is easier to avoid. • Easier decision making, a driver about to enter has one decision: "Is there a vehicle circulating in the roundabout blocking my path?" If not, the driver enters, otherwise the driver waits for a gap. If a collision does occur at a roundabout the impact is much lower due to lower speed and angle of impact. At signalized or stop controlled intersections about 53 percent of all collisions involve left-turn or right-turn collisions. They occur because a left turning driver misjudges the approaching gap in vehicles, and/or the speed of approaching vehicles. Aright-angle collision occur when a driver "runs a red light" or a stop sign and collides with a vehicle using the intersection legally. Neither type of collision is possible at a roundabout. Fatal collisions are unlikely compared to other types of intersections because of lower speed and angle of impact. Operating and Maintenance Costs: Simple signalized intersections cost about $3,000 (US) per year for electricity, maintenance of loops, controller, signal heads, timing plans, etc.. In addition, signal heads and controllers have to be replaced and completely rebuilt on a regular basis. Larger signalized intersections are more expensive to maintain. The only maintenance costs for a roundabout are for landscape maintenance and occasional sign replacement. Construction Costs: Small roundabouts only cost several thousand dollars. Larger roundabouts can cost as much or more than a set of traffic signals. Even if the construction cost for a roundabout is higher than traffic signals, a life cycle economic analysis including construction, operation, maintenance and collision cost reduction of each type of control will usually show the roundabout has a higher benefiUcost ratio. Capacity: The capacity of a roundabout will usually be higher than a signalized intersection because there are no yellow and red times (lost time). Vehicles can enter from each leg simultaneously. At signalized intersections, vehicles can only enter from one or two legs simultaneously as each movement or pair of movements are separated from each other in time. Towards the end of a green phase gaps between vehicles increase. As the vehicle green phase times get longer, headways can get longer, and, as more and more signals are coordinated substantial gaps develop between vehicles. In each case, cross traffic cannot take advantage of these gaps. Whereas a driver waiting at a roundabout can enter any gap in circulating traffic that is large enough. Although the usual assumed gap size for calculation purposes is 4 seconds, many drivers enter gaps as low as two seconds, thereby providing a better level-of-service than the calculated value. Conversely, as the design speed of roundabouts (and hence the speed of circulating vehicles) increases, drivers will wait for larger gaps. A single lane 4 leg roundabout in Daytona Beach, Florida handles 2,832 vph at a high level of service, which is beyond the theoretical value. Delay: Because of the higher capacity of roundabouts, delays are always shorter. Often entering drivers do not stop. Many drivers adjust their speed to take advantage of approaching gaps in circulating traffic, particularly in the off-peak period. If there is no traffic in the roundabout, they don't have to stop. Helps Control Excessive Vehicle Speeds (Traffic Calming): Enforcement of vehicle speeds in residential streets is not cost effective using already stretched police forces. A series of roundabouts will provide effective speed control along residential streets by physically reducing all vehicle speeds. Liability: Traffic signals are a substantial liability for the operating authority. Attorneys often try to prove traffic signals were faulty and therefore the cause of their client's accident. In other words, drivers are not responsible for their behavior because "the traffic signals cause accidents". At awell-designed roundabout, liability for entry collisions rests with the entering driver: the driver failed to yield to the circulating vehicle. In the other common type of collision, the rear-end, the following driver is at fault for following too closely. At a multi-lane roundabout a merge type crash responsibility rests with the driver who incorrectly changed lanes. Self Regulating: Traffic flows change with time and development. To provide optimum operation, traffic signals need to be retimed regularly. As traffic volumes increase, especially cross-traffic volumes, additional intersection lanes need to be added so the intersection capacity can approach that of the mid-block segment. In most cases the whole road is widened. In contrast, the capacity of a roundabout can approach the mid-block capacity of the intersecting roads. Although as the cross-traffic volumes increase, short approach lanes and/or an additional circulating lane may be added. The resulting roadwork and right-of-way requirements are much less than for the signal controlled intersection. Generally a well designed roundabout closely matching approach and mid-block capacity, rarely needs altering, except where the road is widened and the number of approach lanes increased. 1~~~ Congestion Control at Urban Interchanges: The efficiency of roundabouts increases as left turn volumes increase. Vehicles turning left break up the opposing through flow and create gaps for the minor traffic to enter. Urban interchanges with high left turn volumes can be successfully controlled by either a roundabout at each set of ramps or by a large roundabout encompassing the whole interchange, usually within the normal right-of-way. Low Cost Method to Increase Level of Service: Inadequate intersection capacity is the major cause of a road having a low level of service. A roundabout, because of its higher capacity, is a low cost way to increase level of service, especially where left turn volumes are high. Provides Level of Service Without Signalized Intersection Spacing Losses: Traffic signals spaced closer than about one half mile apart create problems in maintaining smooth flow in both directions. A roundabout can sometimes reduce this problem by reducing the number of stops. Provides Equal Access: The timing of traffic signals usually favors the major movement to the detriment of the minor flows. Roundabouts usually provide each driver with an equal opportunity to enter, depending on the availability of gaps, irrespective of the entry location. Improves Perception of Trip Time: The psychological as compared to the actual trip time is perceived to be three times greater for a driver stopped than moving. Roundabouts can significantly reduce stops compared to stop signs and signalized intersections. Drivers will feel less frustrated with the reduction of stop time even if the total travel time is not reduced. Improves Level of Service In Conjunction With Improved Access Management: Medians are an important strategy for access management. But they increase the number of left turn movements at signalized intersections and hence the likelihood of left turn collision. Increased left turn volumes will also decrease the intersection's level-of-service. Roundabouts, in contrast to signalized intersections, become more effective as left turn movements increase, providing a better level-of-service. Left-turn traffic breaks up the approaching traffic flows creating gaps for the minor flow. Improves neighborhood appearance: Speed humps or other neighborhood traffic control devices can be an admission of a traffic problem in the neighborhood. Whereas roundabouts, particularly if landscaped, can be seen as streetscape improvements. Disadvantages of a Roundabout Roundabouts are very effective in many intersections but are not a panacea. They are another useful tool to be considered when designing an intersection or traffic-calming scheme. They are not suitable under the following conditions: The major road carries a very high through volume, with a minimum volume of left turn traffic, and intersecting roads have a low volume. If there are insufficient gaps in the major flow the minor flow will have difficulty in entering the roundabout. In this case, the traffic mix between approaches is not high enough to force the necessary gaps in the major traffic flow. In some cases it may be useful to signalize one approach to a roundabout to create gaps for another leg for an hour or so in one of the peak periods. The traffic volumes are very high, say 6,000 vph. In this case a very large signalized intersection is necessary to separate vehicles in time. Alternatively, an overpass is probably more suitable and safer. This article was originally published on the Internet and is reprinted with permission. Michael J. Wallwork, P.E., Genesis Group, Inc., 8380 Baymeadows Road, Jacksonville, Florida 32256: (904) 730-9360, Fax (904) 730-7165 This article was originally published on the Internet and is reprinted with permission. Michael J. Wallwork, P.E., Genesis Group, Inc., 8380 Baymeadows Road, Jacksonville, Florida 32256: (904) 730-9360, Fax (904) 730-7165 (Genesis Group is a Florida based multi-disciplinary firm whose projects are primarily in the southeast United States, with occasional Caribbean and International commissions. Areas of specialization are engineering, landscape architecture, planning, and surveying.) 7 ~ ` Priorrties, Marker-Ready Technologies and Innovations: Roundabouts Problem: Intersection crashes account for more than 40 percent of all crashes Intersection safety is a serious problem in the United States, and addressing this problem is one of the Federa] Highway Administration's (FHWA) top priorities. In 2001, there were nearly 3 million intersection related crashes, accounting for more than 40 percent of all crashes in the lJnited States. This same year, intersection fatalities rose to 8,876, or 21 percent of all traffic fatalities. In addition, approximately 50 percent, or 1.5 million, of all injury crashes occurred at intersections. Each year, side impacC crashes cause more than one- third of aU vehicle occupant deaths. This type of co0ision occurs must frequently at intersections. Why are there so many intersection crashes? An intersection is, at its core_ a planned point of conflict in the roadway system. With different crossing and entering movements by both drivers and pedestrians, an intersection is one of the most complex traffic situations that motorists encounter. Add the element of speeding motorists who disregard traffic controls, and the dangers are compounded. Who is most likely to be affected? Senior drivers and pedestrians are particularly vulnerable at intersections. Senior drivers (ages 65 years and older) are more likely than younger drivers to cause a fatal crash at an intersection. Putting It in Perspective In 2001: • One intersection-related fatality every hour. One intersection-related injury crash every 30 seconds. • Financial loss of $90 billion fiom intersection crashes. Solution: Roundabouts are a proven, international safety solution that prevent and reduce the severity of intersection crashes Over the past 25 years, U.S. intersection designs and traffic engineering measures have improved, but the annual number of intersection fatalities has not changed significantly. To reduce crashes and improve intersection safety, FHWA recommends the use of roundabouts, where appropriate. Roundabouts must be designed to meet the needs of all road users-drivers, pedestrians, pedestrians with disabilities, and bicyclists. When designing roundabouts, special considerations must be given ~o the needs of pedestrians with visual disabilities who aze unable tojudge adequate gaps in traffic aC roundabouts. Proper site selection and pedestrian channelization are essential to making roundabouts accessible to all users. What is a roundabout and hov~ does its design improve intersection safety? A roundabout is a circular intersection that is designed to meet the needs of all road users- drivers, pedestrians. pedestrians with disabilities, and bicyclists. l ~ Z A roundabout eliminates some of the conflict traffic, such as left turns, that cause crashes at traditional intersections. Because roundabout traffic enters or exits only through right turns, collisions that do occur typically are less severe than those at conventional intersections. A roundabout also is safer than a traffic circle or a rotary, both of which are larger and operate under different traffic rules. The three safety design features of a roundabout are yield control of entering traffic; channelizcd approaches; and geometric entry curvature. These three features are key to the success of a roundabout, because they effectively decrease driving speed (typically to 48 kilometers per hour (30 miles per hour) or less). Unlike a traffic circle or a rotary, a roundabout's incoming traffic yields to the circulating traffic. This creates a safer driving environment than that of traditional intersections. Successful Applications: Roundabouts demonstrate success in reducing crashes Research indicates that well-designed roundabouts can be safer and more efficient than conventional intersections. A December 2002 report by the Maryland Highway Administration indicates that 15 single-lane roundabouts have greatly improved intersection safety in that State. The analysis shows a 100 percent decrease in the fatal crash rate; a 60 percent decrease in the total crash rate; an 82 percent reduction in the injury crash rate; and a 27 percent reduction in the property damage-only accident rate. This report is available for download at http: //safety. fhwa. dot. gov. Benefits • Crashes are less severe than other intersection crashes. • Safer than traditional intersections. • Cost-effective way to improve intersection safety. Additional Resources FHWA has published a comprehensive guide called Roundabouts: An Informational Guide. The information supplied in this document is based on established international and U.S. practices and is supplemented by recent research. Ca11 202-366-59 1 5 to order Publication No. FHWA-RD- 00-067, or download this guide from the Web at www.tfhrc.gov/safety/00068.htm. For more information, contact: Hari Kalla, FHWA Office of Safety Phone: 202-366-5915 E-mail: Hari.Kalla@fhwa.dot_gov F1lWA Research & Technology This page last modified on December 8, 2004 United States Department of "transportation -Federal Highway Administration Source: Federal Highway Administration (FHWA) Research and Technology (R&"[~ (htto://wN~wJhwa.dot.aciv_/rntdu/ti/roundabouts.htm) 2 0~ 2 Thy ~ ~~R~~Ih~n tit~aj a ban :b`~zilrumai~'co 'a b n' ortl<§ BUSINESSREUIEW SER41N0 NEW YORK'9 CAPITAL REOION ham://albany.bizl ournals.com/http://albanv.bizi ournals. corn/ From the July 22, 2005 print edition Roundabouts become DOT's favored solution for problem intersections Joanne McFadden For The Business Review The United Kingdom has been constructing "roundabouts" since 1956, but that type of circular roadway was slow to catch on in the United States, which began building them in 1990. That's changing as those in charge of public roads learn about the benefits of roundabouts. Roundabouts aze designed to eliminate intersections and, hopefully, the potential for accidents. According to the Federal Highway Administration, intersection crashes account for 40 percent of accidents. In 2001, there were almost 3 million intersection-related crashes in the United States. Roundabouts aze not traffic circles, says Peter Graves, a spokesman for the state Department of "transportation, which no longer builds traffic circles. Roundabouts have a "yield upon entry" mle requiring entering drivers to wait until there is a break in traffic to drive into the circle. In many traffic circles, circulating vehicles have to yield the right of way to entering vehicles, or there aze stop signs or signals to control entering vehicles. Through their curved entrances, entry speeds in roundabouts are reduced to 15 to 20 mph. In traffic circles, vehicles will ofren accelerate to join the flow of traffic. David Meager, supervisor of the town of Malta, where five roundabouts will be constmcted over the next three years, said that roundabouts are part of "traffic calming" in that they slow down both circulating and entering vehicles. Meager noted that there are fewer accidents; and because drivers are going at slower speeds, the accidents that do occur are not serious injury accidents like the type that occur at regular intersections. Ed Woods, a partner at Creighton Manninti? En ineering LLP in Colonie, said that roundabouts eliminate "T-bone" accidents, where one vehicle runs head on into the side of another vehicle. John Tozzi, a partner at the same firm, points out the severity of these types of accidents, because sometimes they happen when a car is speeding through an intersection on a yellow or red light. Woods said drivers entering a roundabout are only concerned with looking in one direction (left), when they enter traffic; at an intersection, the driver has to pay attention to traffic from at least three different directions. Another safety aspect of roundabouts is "splitter islands," a feature that resembles a small median, located on all approaches to the roundabout. These serve to divide entering and departing traffic. Proponents tout roundabouts for their elimination of the need for left turns, dedicated Left turn lanes, and traffic signals. "Roundabouts aze designed to keep traffic moving, helping to reduce backups and congestion," DOT's Graves said. Creighton Manning is in the final design stages of a roundabout in downtown Glens Falls, one of the few roundabouts in an urban setting. The roundabout will replace the current five-street intersection near the Civic Center, which rates an "F" on the scale transportation engineers use to rate the efficiency of intersections. The construction is funded 80 percent by the federal government, 15 percent by the state and 5 percent from the municipality. Officials hope that the roundabout will improve traffic flow through this busy area. The Federal Highway Adminstration recommends the use of roundabouts where appropriate, and notes that they must meet the needs of not only motorists, but pedestrians, pedestrians with disabilities and bicyclists. Currently, DOT policy requires highway designers to consider using a roundabout at new or reconstructed intersections, Graves said. However, although roundabouts are a favored solution for problem intersections, they are not designed and built in an ad hoc fashion. "Our designers utilize sound engineering principles to determine if a roundabout would be a palatable solution for an intersection or not," Graves said. They look at traffic rates, high accident rates, the number of lefr toms, and congestion, among other things. To educate New Yorkers, the roundabout design unit of the I)OT regularly makes presentations at public hearings and meetings across the state. The department will also host information sessions for mtmicipalities and groups. The DOT has also advised 12 other states, including California, Massachusetts, Connecticut and Montana, on roundabout design. Town supervisor Meager said the DOT has been very involved in community outreach in Malta. The department has held public meetings, set up a display in the community center, and mailed postcards to residents to familiarize them with the roundabouts. Meager said the town has never taken a position on the roundabouts; because they are being constructed on state roads, but he remains open-minded. He likes that the five roundabouts will be constructed over a period of three years, which will give people time to get used to them. If there are concerns about roundabouts after one or two are constructed, the town will have time to approach the department for discussions. While roundabouts are not a panacea for all intersections, they are becoming widely accepted. "The NYSDOT is very much an advocate of them," Woods of Creighton Manning said. "They're pushing engineers to evaluate them as a means of improving any intersection." ©2005 American City Businees Journals Inc. All contents of [his site ©American City Business ?ow~nals Inc. All rights reserved AMERICAN PLANNING ASSOCIATION ' TRANSPORTATION PLANNING DIVISION ~ ~ ~~TRANSPORTATION- ~aww~w volume XXVII number 4 fall 2002 From the Chair........ Common Misperceptions about Modern Roundabouts by Whit Bdanton, AICP by Wes Butch. Stephen G. Mefzer, A!C't? and Charter R. Owens, ASLA Any success the Transportation Introduction Planning Division has in delivering Relatively new to the United States, modern roundabouts have been common throughout consistent and valuable services to its other portions of the world for several decades as an alternative to stop-controlled and members is based ahnost entirely on signalized intersections. As interest in modem roundabouts has increased in the U.S. the hard work and dedication ofa core and transportation officials have considered their implementation, misperceptions have group of volunteers. In the eight years often arisen. Uuring the course of numerous studies and designs involving roundabouts, I've served as newsletter editor and DLZ has encountered many fallacies which come up with regularity. These opinions are then chair, the activity of the Division typically voiced by members of the public, elected officials, transportation officials, and has waxed and waned, but many consultants who are unfamiliarwith this type of intersection control. This article describes diffecent,members have continued to the most widespread misunderstandings that we have observed during projects involving take on volunteer roles to get things more than 30 different roundabout intersections. done. Over the nextyeazlwouldlike Misperception Number 1: Modern roundabouts are the same as to expand that group of volunteers traffic circles. so that we can continue to enhance This is without a doubt the most our relevance as your professional common fallacy encountered, and organization while increasing the level ,t strongly influences people's of member participation. .rpinions about roundabouts. At Asaresul[ofitsmembers'willingness ,ome point in their lives, most to contribute their time anb energy, people have had bad experiences the Division ~is actively working with large, old style traffic circles on several concurrent projects. Of talso known as "rotaries") such primary importance is the APA Task es DuPont Circle in Washington 'r Force on TEA-21 Reauthorization y g D.C. With their relative) tar e ~ ~ r (see related article in thts issue), diameters, high circulating + in which numerous.TPD members speeds, and merginglweaving Modern Roundabout at the Marsh Road contributedthevtimetodevelopAPA's roquiremenrs, traffic circles often _ Hamilton Road Intersection in Okemos, position. Your continuing input and exhibit poor traffic operations and Michigan (photo courtesy of Dave Sonnenberg assistance will surely be needed as the high crash rates (not to mention brghom ('aunty Road Commission) Reauthorization legislation is debated that driving through them can nextyear.OntheTPDelectionsfront, h-~ unnerving ro uninitiated drivers). Those unfamiliar with modem roundabouts often Todd Barker has stepped forward to aesume that they will cause similar problems since they are also a circular intersection. volunteer as elections chair as we run A Ithough both traffic circles and modern roundabouts utilize round circulating roadways, our first on-line election. there are major differences in the design and operation of these two types of intersections. Planning continues for a single Cue main distinguishing factors are: day airport transportation issues Modem roundabouts have a smaller diameter than most traffic circles, resulting m workshop prior to the APA National lower speeds and safer conditions. Conference in Denver next March Vehicles can enter modern roundabouts much more easily than traffic circles due (see workshop announcement in this to lower speeds on the circulating roadway, flared approaches, proper entry angles, issue). In collaboration with TPD's and the fact that vehicles entering roundabouts always yield to circulating traffic. new Airports Focus Group and Although entry conditions vary among traffic circles, they usually lack most or all of the Advanced Transit Association these characteristics. (ATRA), Division Secretary Larry Properly planned modern roundabous are designed using rigorous standards based on Fabian is assembling a day-{ong specific traffic fuming volumes, while traffic circles are typically sized based on how program dealing with airport land use much land is available and/or road distances needed for accomplishing high speed and transportation planning issues, and weave movements. development density considerations. continued on back continued on page TRAN S PORTAT I ON Pi.aww%w~ MODERN ROUNDABOUTS - continued from page 1 , Misperception Number 2: Modern roundabouts are unsafe. ' , a Often related to misperception number 1 is the belief [hat modern roundabouts are unsafe. Proponents of this view put forth two main arguments to support their claims. First, ,.;rw~ a.3r~,~'~rt~t;~ ;r [hey point to old style traffic circles as an example of what would be expected in terms Whit Blanltln, AICP y g g y publicized roundabout with a of automobile crashes. Second, the sin le out one hi hl R natssance Platttmg Gt~bup' high number of crashes (located in Clearwater, Florida) and presume [hat all roundabouts IOQ-,EastFtne$~ u 4Q1 wdl have the same problems. Having already addressed the first argument above, [he Orlapdd~ ~ ' ~ focus here will be the second. (407 48'1 006 .rrxxt> I ~ The roundabout in Clearwater, Florida, opened at midnight on December 31, 1999 at the (407J 4$7 00$ ~a7rr~ intersection of Mandalay Street, Coronado Street, two other minor streets, and a causeway wblanfon(n~erttegthatvut#k coin connecting the mainland with a barrier island. Since opening, there have been over 500 , r.{ Richard,' t Ison "`¢C crashes at the roundabout, with close to 300 crashes in the first six months alone (the t m ~ ° ' crashes have been relatively minor with few injuries). Over the last two years, the City VtCQ 1 gx • s - Dep~ttmento laq. d of Clearwater has retained an outside roundabout expert to remedy these crash problems. Regional~p[lanuing~~' n After implementing the design and pavement marking changes recommended by this - California ,dl expert, the crash rate at the roundabout has been dramatically reduced. Nevertheless, U~it~ _ h'~ - critics have embraced the situation as an example of what to expect should roundabouts 3801~eY,.°~C` ~ C,8',* be constructed at other intersections in the U.S. The Clearwater roundabout has also Foiu¢'i1`a€ `v``: ~ received coverage in the national media, including an article in the Wall Street Journal (909, 8~4 which sensationalized the crash problem and implied that these problems are typical of (909~.$b~-4 ~r j roundabouts across the U.S. rrwiUson~csutnon `-*5's' <'~~'~,~r'~:-` "e*r_~'' Several important factors are ignored by roundabout critics who fear crash problems like La[ Ir'Akl ~ those experienced in Clearwater First, crash problems are the exception, not the rule, Sec,~t~ * a 32~'` ` at U.S. roundabouts, and the problems at the Clearwater roundabout are not indicative T t ~ of any fundamental problem with roundabouts in general. This is supported by the FO;~ok2$4 '.r Fteld§Cp;ne1;S ; q s large reduction in crashes at the Clearwater roundabout since implementation of design ~ , and striping changes over the past two years. Additionally, the vast majority of U.S. (61'1)$2,~+2~1~~ roundabouts have excellent safety performance. Due to their small diameter (relative to LFa6 Fa1tQ5mrlus tc~o"m traffic circles), low circulating speeds, flared approaches, deflection, and yield-controlled ~ --~E~d.~,2`a,„si,_t ~ `,r = entrances, modern roundabouts are substantially safer than intersections controlled by T. Joseph M~i;lu ,1~Cg traffic signals, traffic circles, and stop signs. Studies from around the world have clearly Treasure r ~ x demonstrated that modem roundabouts typically reduce crashes by 40 to 60 percent EconommD Or, tt4prt) eso}irces compared to stop signs and tratTic signals. They also typically reduce injury crashes by 1136 gVltashin~~f~ u i~~Ath,Fl. 35 to 80 percem and almost completely eliminate incapacitating injury and fatal crashes_ St. Louts,Mf~ , Two recent U.S. studies (Persaud et al 2000; Retting et al 2001) are consistent with these (314}'231-4T1Q'.`~ r results. Considering the massive costs to society related to traffic injuries and deaths, this (3140 621-5191 Pax ~ jmarking(iYa edreonsulting.com is an extremely important benefit associated with modern roundabouts. Linda Howe,zAICP Misperception Number 3: Modern roundabouts cannot handle high Immediate Past Chair traffic volumes. Manager of Technology_Transfer/ Many people, including some in the transportation world, do not realize how many Institute of Tratl5ponaNon-Studies vehicles can be processed at a properly designed modem roundabout intersection. [n UniveriityofCalifoi7tia,Berkeley fact, in most situations, modem roundabouts can accommodate higher traffic volumes 1355 S. 461° Streek Bldg 452 with less delay than traffic signals. A good example that illustrates this situation is the Richmond, CA 94804 ~ Northwestern Connector study in the Detroit suburbs. Completed in 2001, this study (510)231-5678 " compared upgraded traffic signals and modem roundabouts in detail at fourteen highly (510)231-9591Fax~ congested intersections. This comparison indicated that modern roundabouts would Lhowe@kinglet.berkeley.edu decrease motorists' total annual delay by more than 50 percent compared to upgraded Ruth FltZgerald, AICP traliic signals. During the morning and afternoon rush hours, modem roundabouts would Newsletter Editor reduce motorists' delays by about 70 percent on average compared to upgraded traffic President signals. As a result of this study's lied ings., nine high volume modem roundabouts are Fitzgerald & Halliday, Inc. slated for construction by 2005. Additionally, in the United Kingdom, many of the I1 ,000 72 Cedar Street roundabout intersections process henveen 5,000 and 7,000 vehicles dining peak hours Hartford, Connecticut 06106 with low delays_ Beyond these examples, several U.S. communities that have replaced (860)247-7200 stop- and signal-controlled intersections with modern roundabouts have also seen (860) 247-7206 Fax notable reductions in motorist delays. A few illustrations of this situation are: Okernos, rfitzgarald@fhiplan.com ~`L7 0 volume XXVII number 4 fall 2002 Michigan; Santa Barbara, California; and Avon and Vail, Colorado. From the Editor.... ' Misperception Number 4: Any of the popular roundabout software Th;s is my first issue as editor of the programs can be used to analyze and design modern roundabouts TPD newsletter: Iwould-"like to tie with high capacities. able to expound on my goals for the fhe software used to design a modern roundabout can make a major difference in its newsletter.over the-.next year or two, capacity. A number of popular software programs that are used for roundabout design but at this point I freely_admi[ that are based on gap acceptance theory which does not account for all aspects of motorist my only goal so far has been-a short behavior at roundabouts. As a result, these software programs can recommend incorrect term one-[o get this first issue out roundabout geometry, incorrectly calculate capacity, and result in designs [hat provide the door. Now tfiat:.this has become-a poor traffic operations. The alternative to gap theory software is software based on reality, I may indeed tummy attention empirical regression equations. These equations directly relate roundabout geometry to to pondering some longer term goals their capacity and were developed using extensive data collected in [he United Kingdom for the newsletter-.in.[erms of content, for roundabouts operating at capacity. Rodel and ARCADY (both from the United regular features;_ etc.~.I would Jove to Kingdom) are the most popular software programs based on these empirical equations. hear from TPD`-members regarding Roth of these programs produce accurate, reliable estimates of capacity that are directly what "you ~would;.likb to see in the related to geometry. This is crucial when designing roundabouts. newsletter. To that end, please send Misperception Number 5: Modern roundabouts can be properly me an.e-mail and-clue me in. What designed and constructed without special expertise by applying topicsare.ofgreatesCinteres;?.,Which eneral information contained in uidebooks. news items arp''unportant-to you? g g Which azen't?~ What would you like While the guidebooks and manuals available in the U.S. generally provide good to see moreof?:.~. information regarding modern roundabout design, some also contain guidance that is ~ - - - incorrect or that can easily be misapplied. Safety and traffic operations a[ a roundabout In the meantime, with-. -barely a are influenced by design details to a greater extent than a signalized intersection, and moment to'take a. deep breath, it's seemingly minor differences in geometry can greatly affect safety and capacity. As time to start gearing-up'for the next an example, we have seen situations where increasing entry widths by as little as one issue. (Winter 2003); _ tentatively meter changes the overall intersection delay from Level of Service (LOS) D to LOS A. scheduled for distribution in February. The bottom line is that roundabout design should not be undertaken by those lacking Please consider submitting an article experience in this area, especially at intersections with high traffic volumes where multi- for publication.. : This issue has lane roundabouts are needed. several technical articles covering a range of interesting transportation Misperception Number 6: Modern roundabouts won't provide topics: roundabouts, waterborne downstream gaps for motorists turning out of side streets or transportation, wayfinding, and driveways. airfront development. "What is your Except for rare situations, modem roundabouts do create sufficient gaps for motorists to favorite transportation topic? If you turn out of driveways and side streets. Although the random gaps created by roundabouts have a recent interesting project or are typically smaller than those between traffic platoons released from signals, they occur a topic, mode of issue that you feel more frequently and are large enough to allow vehicles to enter the flow of traffic. The sttongly about,- please""submit an way that roundabouts process traffic causes these downstream gaps: traffic circulating article and share your knowledge and within the roundabout has priority over entering traffic (i.e., they force entering motorists experience. As planners, most of us to yield/wait before entering), and this circulating traffic will depart from the roundabout have a broad range of interests. We using different exits. As a result, there is not a constant flow of traffic exiting in any want the newsletter to reflect that one direction. When circulating traffic departs on a different roadway than [he motorist diversity and that balance. waiting to turn out of a driveway or side scree[, a gap is present for that motorist to enter the flow of traffic on the main road. Further assisting the motorist turning from a Finally, a large "thank you" to Whit driveway or side street is the fact that traffic leaving a roundabout is typically traveling Blanton (current TPD chair and about ZO miles per hour. It is possible that in rare cases, extremely high traffic volumes previous newsletter editor) who and certain taming patterns can create problems with downstream gaps. However, in graciously provided advice and these situations, i[ is also likely that similar problems would be experienced with a traffic feedback whenever I needed it (often) signal since right and left turning traffic from the cross road tends to fill the gaps between during the preparation of this issue. Thanks also to the authors of the large platoons of through traffic. technical articles who provided some Misperception Number 7: Modern roundabouts are always more excellent transportation material. expensive than traffic signals. Last, but certainly not least, thanks In some situations, modern roundabouts require more right-of-way at imersections than also to Kelley Kelly for doing all the traffic signals, resulting in higher initial costs. However, in other cases, traffic signals hard work on this issue-the layout. require numerous and lengthy turn lanes (fi>r storage) to achieve acceptable delays. In Ruih Fitzgerald, AICP these situations, traffic signals may require more total right-of-way than roundabouts. November 2002 continued on page 4 -3- TRANSPORTATIONp~aww%wg - ' =sr '~~~t,*° ~+,ars~ * MODERN ROUNDABOUTS continued from page 3 The- Pull o, h trpolrt Additionally, modem roundabouts often solve traffic congestion problems without rik=, ~ 1 -.~s~ ~ requiring road segments to be widened between intersections (known as the "wide . nodes, narrow roads" philosophy 1, resulting in a net cost savings. Another factor worth e e. ~ habl, - consideration is costs associated with crashes. Because they result in far fewer injury and m yep '~t~, 'g' - e gals fatal crashes than traffic signals, modem roundabouts produce lower long-term costs to ? li1~6tis: society as a result of crashes. Also, roundabouts do not require as much maintenance as e ~i~.v ~ . signals and only require electricity for lighting at night. These factors result in long-term ~ 'i. s p=-+-: cost savings. Considering all of these items, modern roundabouts cost more than traffic re i i ~ 0 <~~s signals in some situations, but in others, they are less expensive. a . t~ n ets Misperception Number 8: Modern roundabouts might work in other ~ . ; ew locations, but they will not work with our aggressive drivers. ads It is quite intriguing how every location in [he U.S. where roundabouts are being ' tt ~~f-: considered can simultaneously have the most aggressive drivers in the world (at least - - a~. according to the skeptics we invariably meet on every roundabout project). Nevertheless, .yt~;: this issue is important and requires consideration since aggressive driving does cause -ttlgS- crashes. Aggressive driving affects other motorists regardless of what kind of traffic ,yf'. _ ~ controls are in place. Aggressive drivers are less of a safety threat when intersections r+- ,r~;_ are controlled by modem roundabouts than traffic signals and stop signs because: (I) the potential for head-on and broadside crashes is almost completely eliminated with - roundabouts, and (2) speeds are lower. Modern roundabouts have been implemented 1s}`` with success throughout the world and U.S. Many of these locations have drivers that are t CS: aggressive, and modern roundabouts have worked well. Misperception Number 9: Modern roundabouts are confusing. Modem roundabouts are different from traffic signals and will require drivers to team !~4 .e tt ehC~ how they operate. Experience in the U.S. has shown that motorists quickly adapt to this new type of intersection. Perhaps the best illustrations of this are Vail and Avon, fM r4 ° - seS°, Colorado, [he location of numerous high capacity roundabouts. Both of these cities are tins- major tourist destinations with many thousands of first time roundabout drivers using the ' roundabout intersections each year. A similar situation exists on the campus of Michigan State University where the modern roundabout at the intersection of Bogue Street and or Shaw Lane sees an influx of new inexperienced drivers with each new freshman class. ~'tt~~: Despite large numbers of drivers who have not driven roundabouts previously, these - intersections work well and do not confuse motorists. Additionall ro er use of si nin po ab of a Y, P P g g ~ 'y stt7ct and striping at roundabouts assists motorists and minimizes the potential for confusion. ~~w ~ , ~ .~,~and Misperception Number 10: Older drivers will have a more difficult comm~rs`lta~e au i~'~'acllihes,, time negotiating modern roundabouts than traffic signals. howey~ is qutf~apu ose ttiho , ,r- r^,.. Two comprehensive studies of modern roundabouts in the United States (Betting et al have studte~ the .9 en vaSC`ai~as bem ~ - g 2001; Persaud et al 2000) have shown that the average age of drivers involved in crashes developed'as' hotels, pane ~end`Fida`Jtits, ~t~, ~ - did not increase following replacement of traffic signals and stop signs with modern car~reptatfaciltge$rof~ices, ttaife show rv, ~ roundabouts. Although not conclusive, these results suggest that modern roundabouts do facilities, manu}a-ct4trln~~S~tt~pm~ .,and not pose a problem for older drivers. freight-forwar~der~ ~ at~orts; can begiu;to see wkyth~~`tttt~"atpFront" Misperception Number 11: Modern roundabouts cannot safely will gainadherent$;aswefacetheSssues accommodate high volumes of pedestrians and bicycles. Fa poised"by avtatton.'growt~t fosrtttte.next properly designed modern roundabouts easily accommodate high pedestrian volumes. few decade E~ Yi ~ $ _ The roundabout at the intersection of Bogue Street and Shaw Lane on the campus An airfront is bigger than its airport. of Michigan State University illustrates this point Even with very heavy pedestrian Although amodem airport-itself is an volumes during class changes, both pedestrians and autos move efficiently through this extensive wlleotion'of-runways, -fuel intersection. Auto-pedestrian crash rates are usually also lower at modern roundabouts storage, hangars, tenninals,~ parking, than tral7ic signals. Those pedestrian injuries that do occur tend to be less serious due to and other facilities surrounded by an the relatively low speeds encountered at modern roundabouts. Legitimate concerns have ever-intensifying security fence, it is been raised regarding the ability of blind pedestrians to negotiate roundabouts, and this only the core of the airfront district. topic is under consideration within the 11.5, transportation community. At intersections In part because of the accessibility which are used by blind pedestrians, other countries such as the United Kingdom have provided by major highway and rail implemented design measures including signalized crosswalks with eood success. Where continued on page 5 continued on pale 12 4 TRANSPORTATION - p La vLVL%v~c~ MODERN ROUNDABOUTS - continued from page 4 j appropriate, these measures will promote safe conditions for blind pedestrians. Properly designed roundabouts also safely accommodate bicycles. Studies and experience in Europe have shown that bicycles should not travel within the circulating roadway of m u Iti-lane roundabouts. Instead, bicycles use the pedestrian crossings at a properly designed roundabout. Implementing these measures creates a safe situation for bicyclists. Conclusion Although [hey are not the best solution a[ all problem intersections, modern roundabouts offer substantial benefits in many situations, especially with regard to traffic operations and safety. Common misperceptions about roundabouts have prevented their implementation at some locations where [hey would be the best overall solution to address the problems at hand. Once transportation officials, elected representatives, and members of the public develop a better understanding of the benefits and limitations of modern roundabouts, their use will almost certainly increase across [he U.S. with the result being a more efficient, safer transportation system. References Cited: Modern Roundabout Design for Retting et a12001. RichardA. Retting, BhagwantN. Persaud, Per E. Garder, and Dominique the Red Cedar Road - Wilson Lord. Crash and Injury Reduction Following Installation of Roundabouts in the United Road Intersection -East Lansing, Sates. American Journal of Public Health. April 2001. Volume 91, No. 4. Michigan Persaud et al 2000. Bhagwant N. Persaud, Richard A. Retting, Per E. Garder, and Dominique Lord. Crash Reductions Following InstaNation of Roundabouts in the United Slates. Insurance Institute for Highway Safety. March 2000. Wes Butch is Manager of Transportation Planning and NEPA Services for DLZ, Stephen G. Metzer is ,Llanager of Planning and Ecological Services for DLZ, and Charles R. (livens is Transportation Planning L)ivision Manager for DLZ Michigan. Contact Mr Owens at (517)393-6800 or rowens@dlz_com. SIGNAGE - continued from page 6 techniques for sign production, bringing with them bolder colors, enhanced graphics, new three-dimensional forms, and animation. The newest technology also brings sound and audio to environmental graphics. Although the materials, construction and design of signs have changed dramatically over the years, the purpose of signs remains [he same-- to communicate quickly and effectively. Objectives of Signage Well-designed signage and wayfinding strategies assist in facilitating the design, construction, and management of sites. Well-conceived signage should reflect and enhance the nature and essence of a site and achieve convenience and safety. Signs can also provide a means to reinforce the site values and long-range goals. At a primary level, indoor and outdoor signage should: • Communicate effectively and concisely • Create an appropriate graphic image and identity that is timeless and adaptable • Provide a sense of place in an ever-changing environment • Be attractive, durable and functional • Create a welcoming environment in which people move in an orderly, logical, and safe manner throughout your site • Assist in developing circulation patterns that improve the visitor's ability to navigate and move comfortably within interior and exterior spaces • Be attractive, durable and functional • Provide a means of integration with the development of consistent design standards for site and landscape elements • Achieve convenience and safety • Create a new dimension of experence for the visitor • Complement other elements in the landscape in an elegant and timeless way. d boa[ the Zuthor: Brian Burton is a h/ember of the Standing Committee lin~ technical Evaluations for the Canadian Construction materials Commission and is a regular rnntributar to marry leading landscaping and engineering publications. Ta contact Brian, F.-mail him at- bburion~al[andscape{orwtt ca or crsit www_bba-on. ca P81'd011 US ]n [he Summcr 2002 editum nRhis newsletter we iucnrreclly listed bill Siembieda as faculty advisor to Suzanne Drolel's riward- wnning student paper. also printed m that issue. Suzanne's advisor fur the paper was actually Dr. Richard Lee, AICN, of the Department of Ciry and Regional Planuinp ut Cal Poly. lien Luis Obispo. Our apologies to Ur. Lee. r volume XXVII number 4 fall 2002 • ~ I I I' , I ~ Urban Mobility I I I • Transportation Planning • Environmental Assessments/ V •NEPA/Community Planning Environmental lmpaa Statements ~ • ~ • • Londsrope Ar[hiteAure • Setlion 4(f) 8 5etlion 106 • ' r ' " • • • • Highway/Bridge/Trof(ic • Welland Design/Mitigation _ • _ , _ g g • Land Surrey • Wildlife/Endangered $Decies V • Brvimnmenlol $cieme Assessment • Environmental Engineering • Noise Abatement • Public Works Engineering • Highway Corridor Sludies • Woler/Wastewater • Congestion Management Studies • Ar[hiteaure • Traffic Studies I • Conslruaian AdminisHOtion • Traffic Signal Design ~ O • Construaion testing Services • Traffic Control Design I • Industrial Surveying B Engineering • Roundoboul Sludies/Design i 1425 Keystone Aranue 6121 Huntley Road 2111 E Jefferson Blvd 5 ~ Lansing, Michigan 48911 Columbus, Ohio 43229 South Bend, Indiana 46615 PH. 517-393-6800 PH, 614-888-0040 7H: BOO~B473137 Pox 517-272-7390 Fov, 614-436-0601 Pox 574-136-4471 • M Otlrer otaces located Ihraughout me Midwest `O ` , O 11\~s~.ys;T qN~. ?r Singapore www.dh.cgm Strategic information on new Transportation Planner ~ NEPA Specialist: gLi LINKAGE and MOBILITY Michigan, Inc., one of the Midwest's leading transportation plon- Option5 ning firms, is accepting resumes for an important position within our team Condidgtes for this position should hove the following qualifications: (1) At least three years of experience in transpor- ~ , - , x~ u ~?S tattoo planning or related held, (1) very strong analytical ability ~`i; . 'F~ and independent thinking skills, (3) exceptional writing skills, (4) ~~x -%v knowledge and experience in preparing and writing NEPA and _ ~ planning documents, (5) knowledge and experiente related to y d londuseplanning,naturalresources,andsocio-eronamicissues, ~ ~ ~ ~ ~ =te and (h) knowledge and experiente related to road improvement dab 35~ concepts and traffic analyses. Responsibilities for this position will include: collecting and analyzing information, perform 1 I ' ing technical analyses for specific issues, writing and editing Trans.2 1 NEPA and planning documents, assisting project engineers m the development of conceptual transportation improvements, Loll Wlth yOUr gU0St1011S analyzing and incorporating traffic information into the plan- for afree COnSUltatiOn. ning process, assisting senior stuff with management adiviiies, and coordinating and meeting with clients and team members. LaW rence .I. abian Please send resume and cover letter to: DLZ Michigan, Attn: Hu- ~6I S25_23 l 8 man Resourzes, 1425 Keystone Avenue, Lansing, MI 46911 or, by e-mml, to jkercher~a dlz.mm. T LFabian@compusetve.c°m D L 17- Roundabout Safety Comes to America pg 1, Au[umn 1995, Public Roads Page 1 of 12 Autumn 1995 Vol. 59~ No. 2 All images o/British and , 4 Australian roundabouts have r ' ~ ~ ~ ~ been deliberately reversed to t r `~,3 }a show right-side driving so that ~ t ~ t most Public Roads readers r r ~ ~ r `~sr ~ ~ can better comprehend the r r ~ t ~ x~ ~a~.;~,_ r ~ 1 aYv xi I~ ~'u;e traffic pattern within the ~ ~ Y s ,r ~ ~ roundabout ~r}r~~ rr x._ ~ ~ .t ~ j ~ e _ Roundabout Safety ~ t n ~ ~ Comes to America i The superior safety record of modern roundabouts is well- ~ ' # ; ~ i "~r known in Western Europe and ~ ~ in most British-influenced a~ ':x countries around the globe_ Still many in North America question , ~F`" . ~a9 whether drivers who are : -y ' ~ ~t~~M x > ~ ~ # unfamiliar with this type of ~ ~ r~` 4 ~ ~ ~ ~ ~ intersection can safely adapt to s~ t .~~at ~i~~~ it. But many American highway engineers have become advocates for modern roundabouts, and they are designing and building roundabouts to reduce accidents and increase capacity. Modern roundabouts have recently been built in California, Colorado, Florida, Maryland, Nevada, and Vermont. (1-4) Additional modern roundabouts are proposed for freeway interchanges in Maryland and California, and one modern roundabout interchange was built this summer on Interstate Highway 70 in Colorado. This article takes a look at the roundabout accident experience of America, which began building modern roundabouts in 1990, and of some European countries, where as recently as five years ago modern roundabouts were relatively new. But first What Is a Modern Roundabout? The era of modern roundabouts began in the United Kingdom in 1956 with the construction of the first "yield-at-entry" roundabouts. In 1966, a nationwide yield-at-entry rule launched the modern roundabout revolution. Australia and most other British-influenced countries soon built modern roundabouts. Countries such as the United States, where people drive on the right side of the road, were slower to follow, but many of these countries have been rapidly catching up. For example, roundabouts have greatly increased in number in France since the adoption of the yield-at- entry rule on national routes in 1983. Yield-at-entry is the most important operational element of a modern roundabout, but it is not the only one. Deflection of the vehicle path and entry flare are also important characteristics that distinguish the modern roundabout from the nonconforming traffic circle, which does nol have these characteristics. (See side bar page 48). Other features include sputter islands at all approaches (to control entry speed and deter left turns), good sight distance, good lighting, good signing, no crosswalks across the circulatory roadway, yield lines downstream of the pedestrian crossings, and no parking in the roundabout All of these design characteristics must be met bttp:/,~w~a~w.tlhrc.,,ovipubrds/frtllti~ip95a=! I .htm 1 I /Si200~ Koundabout Salety Comcs to .America pg Autumn 1995, Public Roads Page 2 of 12 for a traffic circle to qualify as a modern roundabout. For example, figure 1 illustrates changing an old traffic arcle to conform to a roundabout design by installing yield signs at all entries and forcing a deflection at the northern entry to the circle. Roundabouts are designed in different sizes to serve various objectives and conditions. Even mini-roundabouts (with a diameter of 25 meters or less) are effective at reducing speed and improving safety. Small to medium roundabouts are 25 to 40 m in diameter. The larger roundabouts (with a diameter greater than 40 m) provide greater separation of traffic and a higher capacity. Why Are Roundabouts Safer? The primary characteristics of the modern roundabout reduce many of the safety hazards of traditional intersections and nonconforming traffic circles. The physical configuration of a modern roundabout, with a deflected entry and yield-at-entry, forces a driver to reduce speed during the approach, entry, and movement within the roundabout. This is contrary to an intersection where many drivers are encouraged by a green or yellow light to accelerate to get across the intersection quickly and to "beat the red light" and contrary to old traffic circles where tangent approaches also encourage, or at least allow, high-speed entries. Another important safety factor is that the only movement at an entry and an exit of a roundabout is a right turn, thus reducing the potential frequency and severity of accidents compared to accidents typically occurring during left turns and when traffic crosses an intersection in perpendicular directions. Modern Roundabouts Spread DeAragao reported on the history of roundabouts. It is thought that one-way circular intersections were invented by a French architect, Eugene Henard, in 1877.(5) During the same period, the American architect William Eno was also proposing his plan for small circles to alleviate traffic congestion in New York City. Since the adoption of a yield-at- entry regulation in 1966 by Great Britain and in 1983 by France, there has been overwhelming interest and research in roundabouts because of the simplicity of their design and operation and particularly because of their safety. Enthusiasm for the safety and high capacity of roundabouts has resulted in a huge increase in the number of roundabouts. By contrast, as growing traffic demand causes nonconforming traffic circles to fail, they are converted to other types of intersections. The Netherlands experienced spectacular growth of roundabouts beginning in the late 1980s.(6) In only six years, approximately 400 roundabouts were built- The reasons given are: a drastic reduction in serious crashes; lower driving speeds through the roundabouts; improved pedestrian crossing facilities; elimination of the need for traffic signals, thus reducing the costs of maintenance and enforcement; and high capacity more than 2,000 motor vehicles and several hundred bicycles and mopeds per hour in one-lane roundabouts. Norway installed yield signs at the entries of all roundabouts in 1985, thus improving traffic flow and reducing accidents.(7) The number of roundabouts in Norway increased to 500 in 1992 (about one roundabout per 8,000 persons) from 350 in 1990.(8) In 1980, there were only 15 roundabouts in Norway. Switzerland adopted the yield-at-entry rule in 1987. (7) The number of Swiss roundabouts grew to 220 in early 1992 from 19 in 1980. (6) Five hundred roundabouts were under study in 1992. By 1987, more than 500 roundabouts had been built in the Brittany and western regions of France. Thereafter, new yield-at-entry roundabouts started "popping up" everywhere in France in new construction and in changing signalized intersections. In 1991, the growth of implementation was at the rate of r,000 roundabouts per year. htto:!/vvww.tthrc.sov/pubrds/fa1195/p9?a4 t.htm I 1 /K/?Of)5 Roundabout Safety Comes to America pg 1, Autumn 1995, Public Roads Page 3 of 12 ;~;i I ~4 ~ , . ~ l - Figure 2 -The North Round- Figure 3 -The South Round- Figure 4 -The conversion of about in the Summerlin area abarrt in Summerlin has an the Long Beach traffic circle of tas Vegas was built in inscribed circle diameter of to a modern roundabout re- 7990. The diareter of the 9f-5 meters and a planned duced accidents and elimi- inscribed circle is 61 rneters, peak hour volume of 6,000 Hated irdernal queuing. and the planned peak hour vehicles. volume is 3,000 vehicles. In Portugal, the implementation of old-design traffic circles was driven by planning, architecture, and aesthetics of public areas, not necessarily for traffic capacity reasons.(9) Traffic circles marked the transitions and limits of the city of Lisbon. Similar to France, they were designed according to Henard's concept. With the uncontrollable increase in vehicular flow, larger and older circles in Lisbon became very congested, forcing the authorities to install signalization. Conversely, in medium- and small-size towns, modern roundabouts were successful because they were economical and did not require signalization. Accidents Fall as Roundabouts Spread to America The first modern American roundabouts were built in the spring of 1990 in Summerlin, a rapidly growing planned _ { community on the west side of Las Vegas. (See figures 2 i==, ° and 3.) With rapid growth of the surrounding community, ° • ~ - -:rt, a daily traffic has increased from very low flows to about 7,000 vehicles in the north roundabout and to about 11,000 Id t ' vehicles in the south roundabout. Only four accidents have _ been reported at the two roundabouts over their five-year history. The first modern roundabout on the California state highway system was installed by the city of Santa Barbara in October 1992. The roundabout replaced an intersection of five two-lane streets regulated by stop signs. The old intersection averaged four accidents per year. Since Since mini-roundabouts allow drnring aver tlreflush installation of the roundabout, accidents have averaged 2.1 or genty domed central island, theycan be installed per year, with only five accidents reported in a 28-month in the smallest ofintersections. Whatever space period (2) is available for truck turns before installation remains available after installation. Maryland's first roundabout was built in April 1993 in Lisbon. The 31.5 -mdiameter roundabout replaced a lightly traveled four-teg intersection regulated by a flashing beacon. The former intersection had averaged eight accidents with eight personal injuries per year.(1) Two accidents occurred in the first three months after construction of the roundabout, resulting in two personal injuries. For the following 21 months, there were no reported accidents. http://www.tflu~agov/pubrds/fal l9>,p9~a41.hhn I 1 /R/~~~~ Roundabout Safety Comes to America pg 1, Autumn ] 99~, Public Roads Page 4 of 12 4 k,.. .w ms .k s ~ { ti I ij 2 cpk. 3 i i} 'I e~{svk~ ~i% i ,.k ~ f N ~ t ~ -tt ~y 4 ~ ~ F° IP ~I~ ":F h yip r 4 ,~-~q 1.+'~ , +r ~.~'4 ~~.Y~. dye ~ .?'si1, ~ " Y ~ } M, {Fka'.~ ~K'..: f.riS ~~f. ~ ~ ~ ~ ~i a: _ i ~ ~ t M..._ . Unlike nonconforming traffic circles, which often permit traffic to enter tangentially at speed, modern roundabouts deflect and slow entering traffic. At this roundabout in England, in the year before it was converted to a roundabout, there were eight serious injury accidents and two fatalities; in the year after conversion, there were no serious injury accidents. The California Department of Transportation (Caltrans) converted the old nonconforming Long Beach traffic circle to a modern roundabout on June 30, 1993. (See figure 4.) Yield signs, stripes, and legends were added to all entries. which were widened to three and four lanes. The circulatory roadway was opened to one unstriped lane 11 m wide in front of the three-lane entries and 15 m wide in front of the four-lane entries. Accidents fell 36 percent compared to the average rate of the previous three years. Accidents with injuries fell 20 percent. Accidents Fall as Roundabouts Spread to Other Countries Around the world, accident rates are falling as roundabouts spread. The Netherlands achieved a 95-percent reduction in injuries to vehicle occupants as many conventional intersections were replaced by modern roundabouts.(10) The fatality rate in the United Kingdom is about half the rate in France 5,000 in the United Kingdom compared to 10,000 in France. Table 1 Causes o1 Reundabo¢i kccidenls in France PERCENT OF - CAUSE OF ACCIDENT ACCIDENTS E-tcriny ;rtt`: fa I:ng to yiv'Iv to n r~ula;'ng tre!fic 3r_6"o L.ac of cows: i~sidc tha ci•cula,o~y roa:iray tci.3`-. P,8551 CO9~IU. EI Ee0Ul0u 1C 0"n. ~9-9r-kYl':1 ACC'G i_riES Hi Q5rrleu -0`S S~Cesvnp,-, iriosaq 3! Pn•,:,= zn!t ~ni's erC~i ry~: 1=. LPn , of r~~.. ~?.9": '+U'~'~i'n: rr. cr :>eu°e,.xr rr; 21 1t9 P:e:; ~:r.~s';:r,:hr„ restl: a a'. o~ aro ortr-os - d n n: rn I 'ir.u n'cr, rex.a:r, rfra I ,.r ~~_~..~.~.-..m..-. ~.,..-~...__.__-___._~..~.v.__._._1 The difference is partally attributed to the use of roundabouts httn:iiwv,tiv.tfhra~~w/pubrds/1~i1195ip9>a41 .htri, 11/K/3005 Roundabout SaYety Comes to America pg I, Autumn 1995, Public Roads Page 5 of 12 since the French and British population and their number of motor vehicles are about the same. (11) In France, where roundabouts were installed mostly in urban areas and their suburbs including residential areas, the safety of roundabouts was generally superior to signalized intersections except where the roundabouts were large with wide entries or where there was extensive bicycle traffic. The accident rate on rural roads was clearly better for roundabouts than for major/minorjunctions regulated by stop or yield signs. The average rate of reported injury accidents per 100 million vehicles entering major/minorjunctions was 12. This was three times higher than the rate for roundabouts where there were only four accidents per 100 million vehicles.(12) Numerous one- ortwo-lane roundabouts have been built recently in Germany, but several large old-style traffic circles remain. Researchers investigated 14 circular intersections and 14 non-circular intersections near the circular intersections. The numbers of accidents per million vehicles were: (13) Old traffic circles Signalized intersections Smaller roundabouts 6.58 3.35 1.24 The most extensive roundabout accident analysis in Norway was conducted In 1990. Accident records from 1985 to 1968 at 59 roundabouts and 124 signalized intersections were examined The comparative accident rates, in numbers of reported accidents per hundred million vehicles, are given below: (8) Number of Legs Roundabouts ~ Signalized Intersection f 3 ~ 3 5 4 Besides safety benefits, other advantages to roundabouts were demonstrated. Speed reduction, moderation of traffic flows in favor of through traffic, use of the central island to mark the transition from one class of road to another, and improved capacity are "products" of roundabouts. Studies of British mini-roundabouts, which often have two- orthree-lane entries even though the central islands are less than 4 m in diameter, indicate that larger roundabouts are generally safer.(14) However, recent studies of mostly one-lane mini-roundabouts in continental Europe found a lower accident rate at mini-roundabouts than at larger roundabouts. Studies in Switzerland and France identified the following benefits of mini -roundabouts:(15,16) Flow improvements. Reduction of conflicts/accidents Reduction of speeds upstream, through, and downstream of mini-roundabouts. Adherence to the yield-at-entry requirement Reduction of noise (as a result of the reduction of speed). http:/hvww.tthrc.guv/pubrds/CaIl9 ~/p95ua l .htm 1 I /8/'00 Rotimdabout Safety Comes to America pg 1, Autumn 1995, Public Roads Page 6 of 12 Heightened awareness of drivers as they were forced to reduce speed. Safety of Roundabouts for Pedestrians and Cyclists While modern roundabouts have long been considered safe for pedestrians, the record for bicycles and motorcycles has been mixed. According to one study in the United Kingdom, 15 percent of all intersection accidents in 7984 involved at least one bicyclist, but 22 percent of all roundabout accidents involved at least one bicyclist. (17) In contrast, British mini-roundabouts do not appear to be particularly dangerous for bicyclists. A survey in 1989 of mini-roundabouts in England, Scotland, and Wales found that the crash-involvement rates of motorcycles and bicycles in 50-km/h (kilometers per hour) speed zones was about the same for four-leg mini-roundabouts as for four- leg signalized intersections. However, the rate for cars at the mini-roundabouts was much lower than at the intersections: Crash-Involvement Rates (per 10 million of vehicle type) Signalized Intersection Pedal Cycle Motorcycle Car 175 240 48 Mini-roundabout Pedal Cycle Motorcycle Car 189 237 27 hug:.'iwww.tfhrar?ov;pubrds/ILI195/p9?a~ll.htm I l/8/.'_00 Roundabout Safety Comes to Amcrica pg 1, Autumn ] 995, Public Koads Page 7 of 12 t; `f ~b ,v+~ . i s ~'i .r- t~~. sSu F~a c: s9r~~ w~r I ire an.* ~ ?a C a H { n...~ ~ . "~,SK%~' 4~. tr - ~~..,i n~~~ d ~ . f i',~~ ~ ~ ro'~ t'r The flared entries of modern roundabouts give them a high capacity in compact space. At this multilane entry, a vane island between the second and third lanes deflects the trajectories of vehicles in the outer lanes. Contrary to the British experience, a recent study in the Netherlands of 181 mini-roundabouts that were converted from three- and four-leg intersections found injuries to bicyclists decreased on average from 1.30 casualties per year to 0.37 casualties per year a 72-percent reduction. (10) In Europe, bicyclists at roundabouts were handled in one of three ways: bicyclists mix with motor vehicles, bicyclists have a separate lane, or bicyclists have a separate bike road. The bike road provided the best protection for cyclists, and, perhaps surprisingly, the bike lane was the least safe option because this design requires the motorists and bicyclists to cross paths. (See figures 5 and 6.) Accident Investigation in France In 1990, 202 accidents were investigated at 179 urban roundabouts in France. Table 1 shows the relative frequency of the different causes of these accidents.(18) The major design recommendations derived from the above study are: Ensure motorists recognize the approach to the roundabout. Avoid entries and exits with two or more lanes except for capacity requirements. Separate the exit and entry by a splitter (ghost) island. Avoid perpendicular entries or very large radii. Avoid very tight exit radii. Avoid oval-shaped roundabouts. }~ttpalwww.tlhrc.gov/pubrdslCall9_ilpJSaa l .hun I l /8!2005 Roundabout Safety Comes to America pg 1, Auhunn 1995, Public Roads Page R of 12 - ~t ry o-~;~yy ~ w:~?)r°AE p e6 1t~ 1 ft 4ds~~%s C 4 1ti x~ ~ ,i i} r ut t' ~ ~Ff r,.. ~r... , € ~ ~r ~ c".y; ~ M ;tY` S~ , Compared to signalized diamond interchanges, modern roundabout interchanges are safer and more efficient. A modern roundabout on each side of the freeway keeps the traffic flowing, eliminating the need for storage lanes. Thus, fewer lanes are needed on the most expensive element of the interchange -the overcrossing. ; A j u Il i~~i -'-i II~ it =n - _ ~ ~.x ~ Figure 5 - r>f the three options to Figure 6 K bicycle and motor accarnmodate bicycle traffic in vehicle volumes are high, a peri- roundabacrts in the Netherlands, pheral bicycle read is recommen- roundabouts with a separate bi- Bed. (The shaded areas repre- cycle lane have the highest acci- sent the bicycle roads.) dent rate for both motor vehicles and Bicycles. (The shaded areas represent bicycle lanes.) A study of roundabout lighting in France found that nighttime accidents are relatively rare and most accidents involve property damage only. The study recommends that the lighting design should be based on a perception process: remote perception at about 250 m, approaching perception at about 100 m, and entry perception at the entry.(19) Conclusion Modern American roundabouts have produced remarkable safety records. Since this experience is similar to the roundabout experience reported in other parts of the world, the safety of roundabouts compared to signalized intersections and old traffic circles has been well established. As a result, the number of roundabouts in the United States is expected to increase geometrically in the next decade. References hnnaivc~•~~~.tflira~,oc/pubrdsq~u 1195/p95a-l i .htm l U8~ 'OOS Roundabout Safety Comes to America pg 1, Autumn 1995, Public Roads Page 9 of 12 (1) E.J. Myers. Press release on Lisbon, Md., roundabout; Hurst-Rosche Engineers, Cockeysville, Md., April 13, 1995. (2) P. Wessel. Information transmittal from Santa Barbara Public Works Department to Peter I. Doctors, March 16, 1995. (3) J. Goodway. Report by the Las Vegas Public Works Department, May 4, 1995. (4) L. Ourston. "Nonconforming Traffic Circle Becomes Modern Roundabout," Unpublished report to Caltrans, October 1994. (5) P. DeAragao. "Circles and Roundabouts: An Historic Review," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted by the Institute of Transportation and Planning, Swiss Federal Institute of Technology, Lausanne, Switzerland. (6) P.H. Bovy. "Spectacular Growth of Roundabouts in Switzerland: From 19 to 720 Roundabouts in 15 Years," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted by the Institute of Transportation and Planning, Swiss Federal Institute of Technology, Lausanne, Switzerland. (7) A. Dagersten. "Roundabouts in Switzerland and Sweden, Thesis 72," Department of Traffic Planning and Engineering, Institute of Technology, University of Lund, Lausanne, Switzerland, 1992. (8) T. Giaever. "Application, Design, and Safety of Roundabouts in Norway," Actes du Seminaire "Giratoires 92," Nantes, France, Oct. 14-16, 1992. Research conducted by the Foundation for Scientific and Industrial Research at the Norwegian Institute of Technology. (9) F. Nunes da Silva. "The New Roundabouts in Portugal," Actes du Seminaires "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted by the Graduate Technical Institute, Lisbon, Portugal. (10) C. Shoon and J. Van, Minnen. "The Safety of Roundabouts in the Netherlands," Traffic Engineering and Control, March 1994, pp. 142-148. (11) Lauer. Center for Urban Transportation Studies, France. (12) T. Brenac. "Roundabouts in France: Development, Level of Safety," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted at the National Institute of Research on Transportation and Safely, Provence, France (13) W. Brilon and B. Stuwe. "Roundabouts in Germany: Recent Results Regarding Capacity and Safety," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. (14) G. Maycock and R.D. Hall. Accidents at 4-Arm Roundabouts ,Transport and Road Research Laboratory, United Kingdom, 1984 (15) P. DeAragao. "Mini-Roundabouts in Switzerland," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14 16, 1992. Research conducted at the Institute of Transportation and Planning, Swiss Federal Institute of Technology, Lausanne, Switzerland. (16) B. Guichet "Mini-Roundabouts in France," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted by the Center for Technical Studies of the Western Facilities, Nantes, France. (1?) R.E. Layfield and G Maycock. "Pedal-Cyclists at Roundabouts," Traffic Engineering and Control, June 1986, pp. 343-349 (18) B. Guichet "Classification of Accidents on Urban Roundabouts," Acles du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted by the Center for Technical Studies of the Western Facilities, Nantes, France. http://ww~'.tlhrc.go~~/pubrds/fall9~/p9~a41.htm 1 I /R/2005 Rowidabout Safety Comes to America pg 1, Autumn 1995, Public Roads Page 10 of 12 (19) J. Menard. "Lighting of Roundabouts," Actes du Seminaire "Giratoires 92,"Nantes, France, Oct. 14-16, 1992. Research conducted by the Center for Technical Studies of Facilities, Normandie, France. Leif Ourston is president of Ourston & Doctors, a highway engineering firm in Santa Barbara, Calif., that specializes in modern roundabouts. He designed America's first modern roundabouts (in Las Vegas), Maryland's first modern roundabouts (in Lisbon and Gaithersburg), America's highest capacity modern roundabout (in Long Beach, Calif.), and America's first modern roundabout interchange (in Vail, Colo.). He wrote Caltrans"'Modern Roundabout Guidelines," and he is advising the Florida Department of Transportation on a modern roundabout program. Joe G. Bared is a professional civil (transportation) engineer in the Design Concepts Research Division of the Federal Highway Administration. He manages research contracts and conducts staff research. Currently, he is developing accident prediction models for the Interactive Highway Safety Design Model. He is also pursuing a doctorate in transportation engineering at the University of Maryland. Modern Roundabout or Noncoforming Traffic Circle? Unlike nonconforming traffic circles, modern roundabouts conform to modern roundabout guidelines. Among other important new features, modern roundabouts have yield-at-entry, deflection, and (often) flare, as illustrated below. Modern Roundabout Nonconforming Traffic Circle Entering traffic yields fo circulating Entering traffic cuts off circulating traffic. traffic. Circulating traffic always keeps Circulating traffic comes to a dead moving. stop when the circle fills with entering traffic. Works well with very heavy Breaks down with heavy traffic. traffic. Long weaving distances for No weaving distance necessary. merging entries cause circles to Roundabouts are compact. be large. ,F ~~E~Y, ~ Yield-at-Entry Entering traffic aims at the center of Entering traffic aims to the right of the central island and the central island and is deflected slowly proceeds straight hu,,.:,..~.,,.. ~17,~.~ ~.,..,/n,~},r.i~/(~~II~);n5e11 ht.p l lihi2U0> Roundabout Salety Comes to America pg 1, Autumn ] 995, Public Roads Page 1 I o1 12 around it. ahead at speed. Slows traffic on fast roads, Causes serious accidents if used reducing accidents on fast roads. Deflection promotes the yielding Fast entries defeat the yielding process. process. I I yT~ r Zy 1 ! 'i j 1 Deflection Upstream roadway often flares at entry, Lanes are not added adding lanes. at entry. Provides high capacity in a Provides low capacity even if compact space. circle is large. Permits two-lane roads between For high capacity, requires roundabouts, saving pavement, multilane roads between circles, land, and bridge area. wasting pavement, land, and bridge area. Flare hup://www.tlhrc.gov/pubrds/lall'>~/p95a41.hUn 1 1 /8/?005 Roundabout Safety Comes to America pg 1, Autumn 1995, Public Roads Yage 12 of 12 ~a:,~p ~ ` ~ , ~ t y y .r t 4Q YSA I~ ~ n~Y~ 'f.n ~ u: r x S"ii: ~I I ,L ~ t ~ `tie ;,z' _ „ ~T~ w << 9 ~i~ ~ t`t ~ _ ~ ~ ,;m. ti~ / ~ "`z~, tea: a~ a .w ~ ~s Since its installation in November 1992, the Five Points roundabout in Santa Barbara. Calif., has reduced accidents, confusion, and delay. i~ ~Hw~ TFHRC Home ~ FHWA Home ~ Feedback United States Department of Transportation -Federal Highway Administration httn~/ha ~ w_t fhrc.eo~ i uuhrds/tall9>/n95a41 . hun I I /8i _i 105