MATC Fall Lecture Series: Eugene Russell
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This document summarizes a seminar presentation about roundabouts. The presentation discussed why roundabouts are safer than traditional intersections with traffic signals or stop signs, providing statistics showing large reductions in crashes and injuries at roundabouts. It covered design elements of modern roundabouts that contribute to safety, such as deflection and low entry speeds. The presentation also addressed concerns about pedestrian, bicyclist, and visually impaired accessibility at roundabouts and showed how well-designed roundabouts can improve safety and traffic flow for all users. A brief history of roundabout development in various countries was presented as well.
![U.S Single-Lane Roundabout Crashes- Insurance
Institute for Highway Safety (IIHS) Study Results
(IIHS) study [Persaud, et.al., 2001]
Highly significant reductions of approximately
40% for Overall Crashes
76% for Injury Crashes
90% for Fatal and Incapacitating Injury Crashes (predicted)](https://image.slidesharecdn.com/roundabouts101-121205091930-phpapp02/85/MATC-Fall-Lecture-Series-Eugene-Russell-41-320.jpg)
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MATC Fall Lecture Series: Eugene Russell
- 1. MATC Seminar , September 14, 2012 Dr Eugene R (Gene) Russell PE, PHD Professor Emerius, Kansas State University
- 2. Today’s Presentation Why Roundabouts ? Intersection safety statistics Circle Differences Safety examples Latest roundabout crash statistics Pedestrian/ Bicycle safety Visually impaired concerns & PROWAG Benefits other than safety Some history- IF TIME PERMITS
- 3. Objective To be honest; give you reason to love roundabouts !
- 10. FATALITIES 2010: 32,885 fatalities, rate=1.11 vs 2002: 43,005 fatalities, rate = 1.51 per 100MVM
- 11. INJURIES 2010 2,239,ooo injured vs 2002 2,926,ooo rate 102 vs 75 per 100MVM
- 13. Traffic Signal Stop Sign % vehicles, all 26.6% 6.9% crashes
- 16. RED LIGHT RUNNING Preliminary estimates for 2001 indicate 200,000 crashes, 150,000 injuries, and about 1,100 deaths were attributed to red light running. This is down to around 800 deaths in 2010 The use of RLR cameras very controversial
- 18. RLR Crashes http://www.youtube.com/watch?v=NC-rimCfu50
- 19. Red Light Running Crashvideos http://www.bing.com/videos/search?q=red+light+runni ng+videoo&view=detail&mid=5E92E1DA7FD1B5AEFE1A 5E92E1DA7FD1B5AEFE1A&first=0&qpvt=red+light+runn ing+videoo
- 20. My Main Point Traffic Signals and Stop Signs are not as safe as public thinks
- 21. What is a Modern Roundabout Or, What is it Not ?
- 25. Lane flow example lane Flow Example http://www.ourston.com/resources/webcams/halifax.ht ml What about signing?
- 27. Traffic Circle vs. Roundabout Kingston Traffic Circle Under Construction to become a Roundabout
- 28. Traffic Circle vs. Roundabout Malta Roundabout superimposed on Latham Traffic Circle Tangential Approach geometry vs. Deflected Approach geometry Clearly defined exit
- 29. Traffic Circle vs. Roundabout Johnson City Traffic Circle becomes Roundabout R C
- 30. NOT a Roundabout
- 31. Quick Comparison: Circle, rotary Modern Roundabout 40- 50 mph 15 – 25 mph Speeds 65-80 km/h Speeds 25-40 km/h Diameter > 60 meters Diameter < 60 meters About 200 ft About 200 ft High speed merge can Safer, low-speed, be confusing and adequate deflection Clear yield at entry
- 32. IIHS Video
- 35. Classic diagram 8 4 8 4 16 0 32 8
- 36. Pedestrian conflicts Conventional intersections; potential vehicular conflicts, each coming from a different direction: 1. Left turn, through and right turn movements from the leg of the intersection the pedestrian is crossing. 2. Through movements coming from the opposite side of the intersection. 3. Right turns from the cross street. 4. Left turns from the cross Street. 5. Right turn on red
- 37. Signalized intersection vehicle pedestrian conflicts
- 39. vehicle pedestrian conflicts at single Lane roundabout
- 40. Conflict points for T intersections
- 41. U.S Single-Lane Roundabout Crashes- Insurance Institute for Highway Safety (IIHS) Study Results (IIHS) study [Persaud, et.al., 2001] Highly significant reductions of approximately 40% for Overall Crashes 76% for Injury Crashes 90% for Fatal and Incapacitating Injury Crashes (predicted)
- 42. Using IIHS Figures Roundabouts have: Potential to save motorists: Hundreds of thousands of injury crashes Thousands of deaths
- 43. Benefits of a Roundabout SAFETY, particularly injury crashes and fatalities Including safer left turns (all right turns) More efficient traffic flow Increased capacity for given level of demand Less vehicle air pollution Pedestrian safety Access management
- 44. Benefits of a Roundabout (Cont’d) Community Benefits Aesthetics/ Landscaping Walkability/Village Atmosphere Neighborhood Traffic Calming (secondary benefit) Catalyst for Smart Growth Lower life cycle costs at many intersections
- 45. FHWA Roundabout Guide 2nd ,NCHRP 672, and 1st ed , NCHRP 572 Exh. 5-9
- 46. Hutchinson, Roundabout The Hutchinson News “If you do build a roundabout it will be the ‘Mother of all Bad Intersections’. We could sell tickets to see it.” “They are easy to find; just look for a traffic jam and the ground piled up with broken glass and car parts.” CARS Organization
- 48. Hutchinson, KS, 23th and Severence
- 50. Maryland Roundabout Mean Crash Rate Crashes per million entering vehicles Before After Total 1.53/MEV 0.97/MEV Injury 0.48/MEV 0.11/MEV
- 51. Before and After Mean accident Rates- Maryland Roundabout
- 52. Safety problems correctable by roundabouts Right angle, head-on, left and through, and U turn conflicts. High crash severity – injury or fatal. Sight distance or visibility problems that reduce the effectiveness of stop sign control. Inadequate separation of movements on some approaches Red light running
- 53. Statement from Discover Magazine Around 2000 :“The modern roundabout may be the safest most efficient traffic control device available today.” I say it is !
- 54. Caveats Safety and efficiency achieved by a well designed roundabout keys: Deflection Low-speed Lane continuity
- 56. Pedestrian Safety Major studies have found no fatalities at US roundabouts Cross one lane at a time- single lane Cross traffic going in one direction at a time. Less likely to be killed at low speeds Actually very little US data on pedestrian safety Worldwide, roundabouts show increase in pedestrian safety
- 57. Australian Roundabout Information Melbourne, AU 1970- 3 Roundabouts 2002- About 3000 Source: Andrew O’Brien
- 58. Australian Roundabout Information contd.. Traffic signals 1996 - 2000 1460 Crashes involving pedestrians 41 Fatalities 611 Serious injuries Source: Andrew O’Brien
- 59. Australian Roundabout Information contd.. Roundabouts 1996 - 2000 1097 Crashes 57 Involved Pedestrians 0 Fatalities 32 Serious-requiring hospitalization Source: Andrew O’Brien
- 60. Sample Single-Lane Roundabout Pedestrian Facilities
- 61. Increased vehicle storage (number of vehicles a function of distance of exit lane crosswalk from circulating lane. ) In VISSIM prelim results, 20, 60 100 vehicle storage for proximal, zig zg and distal
- 62. Visually Impaired Access Board recommendations -Engineering judgment for now; at least not enforceable standards PROWAG ( Public Right of Way Accessibility Guidelines) Blind difficulties: finding/aligning crossing, judging traffic flow, evaluating gaps. Issues at roundabouts Wayfinding to set back crossing Traffic flow sounds not clear Gap Creation without stop condition Gap Detection not as clear as at stop control
- 63. ADA and the Access-Board Around 2000 declared roundabouts not accessible. Draft language would have required pedestrian signals on all legs of all roundabouts. Later drafts require pedestrian signals on all legs of two or more lane roundabouts. Have indicated all along that full, green, yellow, red signals not necessarily required A-B latest language OKs HAWK (pedestrian hybrid signal )– or equivalent control that will make roundabout crosswalks accessible to blind pedestrians. ???????
- 64. Pedestrian Hybrid Signal-many still call HAWK
- 65. Hawk being researched in Lawrence, KS - UTC project
- 66. KSU Studies Researchers at Kansas State University (KSU) have been studying the operational performance of modern roundabouts since 1997
- 67. Candlewood & Gary, Manhattan, KS
- 68. KSU Roundabout Performance The primary focus of this research was to study the operational performance of 11 Kansas roundabout s The research focused on eleven sites with different traffic volume ranges where a modern roundabout has replaced or built instead of a Stop or Signal controlled intersection
- 69. KSU Studies contd.. Results of studies for Kansas DOT at several roundabouts indicate that the operational performance of roundabouts is better than TWSC, AWSC and Signalized intersections at all locations studied
- 70. KSU Studies contd.. Helped to establish that even at relatively low traffic volumes, modern roundabouts could be beneficial as a traffic control device at an intersection
- 71. Kansas Average-Operational Performance Measures Of Effectiveness Before R.A % Diff. Average Intersection Delay (Seconds/Veh) 20.2 8 -65% Max Approach Delay (Seconds/Veh) 34.4 10.4 -71% 95% Queue Length (Feet) 190 104 -53% Degree Of Saturation- Intersection (v/c) 0.463 0.223 -53% Proportion Stopped- Intersection (%) 58 29 -52% Max Prop. Stopped (%) 62 37 -42% Before: Signal/AWSC/TWSC, RA: Roundabout
- 72. Emissions Major pollutants Carbon monoxide (CO), Carbon dioxide (CO2), Oxides of nitrogen (NOx), Particulate matter (PM10 ,PM2.5) Hydrocarbons (HC) or Volatile Organic Compounds (VOC) Modern Roundabouts cut emissions
- 73. Kansas Average-Environmental Impact Measures Of Effectiveness Before R.A % Diff. Carbon Monoxide (CO) Kg/hr 10.79 7.26 -33% Carbon dioxide (CO2) Kg/hr 237.30 127.59 -46% Oxides of Nitrogen (NOx) Kg/hr 0.348 0.225 -35% Hydrocarbons (HC) Kg/hr 0.446 0.210 -53% Before: Signal/AWSC/TWSC, RA: Roundabout
- 74. KSU/IIHS Study- Delay & Proportion Stopped Kansas, Maryland & Nevada TWSC (Before) vs. Roundabout (After) About 20% reduction in total delay 13% to 23% reduction in delay per vehicle 14% to 43% reduction in proportion stopped
- 75. ENERGY- Gasolene Usage Another IIHS study of 10 signalized intersections: If converted to roundabouts: Each vehicle delay would be 1 minute less Annual delay savings 325,000 hours Fuel savings, 235,000 gallons/year
- 76. Bicycle conflicts Conflicts experienced by bicyclists that roundabouts are dependent on how they choose to negotiate the roundabout. This is similar to conventional intersections. For experienced cyclist riding through the roundabout conflicts are similar to those at signalized intersections. For those using the bike ramps and using the crosswalk, complex or similar to those of a pedestrian. A bicycle – pedestrian conflict is also possible. USA experience with bicycles is very limited.
- 78. Netherlands- Geometric design for a roundabout that gives cyclists right-of-way
- 79. Netherlands- Geometric design for a roundabout that does not give cyclists right-of-way
- 80. Public Acceptance Generally poor- initially Confusion with Old circles, rotaries Sometimes small circles Heard or experienced lots of bad things about large, old circles Lots of misinformation “out there”- roundabout myths, I call “irrational opposition” Don’t like change Don’t like speed control (small circles)
- 81. Public Acceptance Improves With Experience Survey by IIHS Feeling about Roundabouts BeforeAfter Strongly/Somewhat Favor 31% 63% Strongly/Somewhat Oppose 55% 28%
- 82. Conclusion At most intersections with significant cross traffic and turning movements the modern roundabout is the safest most efficient form of intersection control available today. After construction attitudes change to more positive Public needs more education
- 83. DEFLECTION ?
- 84. Flannery (2000) Study of Roundabout Crashes Main Causes: 1. Approach geometry allowing high speed, and 2. Lack of adequate deflection in the roundabout
- 85. New Zealand Safety Audit Study (Most common problems) One of the most common: Inadequate deflection as motorists approach the intersection
- 86. History Circular Intersections Circular places at the convergence of Roads since Middle Ages Examples Paris, Arc de Triomphe (history continued)
- 87. Gyratory Operation- around1900 Eugéne Hènard, “Giratoire-boulevard” Place Ch. d’Gaulle (1907) Wm. Phelps Eno, Columbus Circle (1904) S.J. Hellier, Great Britain (1901) suggested a gyratory road system (history continued)
- 88. London, Gyratory Systems introduced, 1925-26 One way systems around existing squares “circus” idea (Brown) “gyratories,” “rotaries,” “traffic circles” (history continued)
- 89. Driver education SLOW DOWN Watch for pedestrians Single lane- should be no problem Multilane- get in right lane on entry ! Design should provide lane continuity. At traditional intersection, Most drivers would not turn right from the left lane or change lanes in the intersection or anywhere without looking, signaling and finding a gap, BUT MANY DO IT IN ROUNDABOUTS ! WHY ?? I believe drivers losing respect for YIELD everywhere
- 90. Great Britain roundabout development to 1966 Worked poorly-large queues, locking Bigger and bigger designs – weaving Did not end jams Compromised safety Intolerable by 1966 Almost gave up on them (history continued)
- 91. Give Way Rule (Yield at entry), 1966 Ended locking Improved capacity Reduced crashes Total change in design philosophy (history continued)
- 92. US History Massive road building in 1930’s Gyratory intersections generally called “traffic circles” were no advantage Lost favor By 1950’s no longer considered viable Several “bad” circles still exist (history continued)
- 93. Early US Designs Large Priority at entry High speed entry Weaving in circle/confusing High crash rates Important re-current acceptance (history continued)
- 94. Great Britain, Post 1966 1975, revised design guidelines Introduced concept of “deflection” Islands at entry (splitter islands, generally raised ) and central island (history continued)
- 95. 1984, Design Standards about like todays Entry path curvature standards Concept of newer, smaller roundabouts as a “normal” roundabout Prefer modern roundabout Could say 1984 was birth of the modern roundabout world wide (history continued)
- 96. US Modern Roundabout Growth First in early 90’s 90 in 1995 About 3000-4000 today In Kansas: ONE in 1997; about 175 today in operation, being built or planned.; 6 on major state highway intersections. (end history)
- 97. Conclusions Statistically significant reductions in delay, queueing, stopping and emissions At most intersections with cross traffic and turning movements – a modern roundabout is the most viable alternative for safe, efficient vehicular traffic, especially for reducing injury crashes and deaths ! In new areas, after construction public attitudes change to more positive Public needs more education
- 98. My Belief Roundabouts are the safest most efficient form of intersection traffic control available today !
- 99. The End
- 100. Eugene R(Gene)Russell Sr.,PE, PhD, Professor Emeritus of Civil Engineering, Department of Civil Engineering, 2118 Fiedler Hall Kansas State University, Manhattan, KS 66506 Ph . 785 539 9422; Fx 785 532 7717; Cell. 785 410 5231 email. < geno @ ksu . edu >