MATC Fall 2012 Lecture Series

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
!

4. Intersection Crashes
http://www.nhtsa.gov/nhtsa/announce/speeches/030503Peters/FHWA-AASHTO030602.pdf

5. Intersection Crashes contd..
http://www.nhtsa.gov/nhtsa/announce/speeches/030503Peters/FHWA-AASHTO030602.pdf

6. Intersection Crashes contd..
http://www-nrd.nhtsa.dot.gov/pdf/nrd-30/NCSA/Rpts/2003/2002EARelease.pdf

7. Intersection Crashes contd..
http://www-nrd.nhtsa.dot.gov/pdf/nrd-30/NCSA/Rpts/2003/2002EARelease.pdf

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

17. Red Light Running

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 ?

24. Old Traffic Circles

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

38. Conflict Point Comparison

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.

77. Bicycles Provisions contd..

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 >