An Overview of Modern Roundabouts
and
What they Might Soon Mean for You
Ken Sides, P.E, PTOE, AICP
Workshop on Roundabouts
University of Florida
Transportation Research Center
Maitland, Florida, August 18, 2009
Is Round Right for your Traffic Engineer? Suitability Checklist 10-20% capacity increase; better peak LOS LOS A & B during off-peak hours (22 hrs/day) Free-flow 8-10 hrs/day Crashes -65%, injury crashes -76%, injuries much less severe, fatalities down 90-100% Much less exposure for pedestrians Much better LOS for pedestrians
Is Round Right for Access Management Projects? Suitability Checklist Intersection establishments get access – Finally! Driveways into roundabouts are OK Continuous medians are practical Continuous parking OK, even angle parking Green attracts customers, investment No more worries about signal spacing, signals for shopping centers
Are Roundabouts Right for Environmentalists? Suitability Checklist Less impervious area (asphalt) More vegetation 25-30% less fuel consumed 25-30% less toxic emissions 25-30% less greenhouse gases
CMAQ federal funding for Congestion Mitigation & Air Quality improvement: $1 Billion annually
Are Roundabouts Right for Children?
Suitability Checklist Much slower vehicle speeds Much less exposure:
1/3 as many ped/vehicle conflicts Pedestrian refuge on splitter island
Shorter distance; shorter time Cross only one lane at time, only one direction at a time
Much less complexity All these benefits apply to elder peds, too
Are Roundabouts Right for Older Users?
Suitability Checklist Reduced demands for:
Visual acuity Concentration Reaction time Neck/trunk flexibility
Much lower, safer vehicle speeds
Events play out slowly Everyone has time to adjust No demands for split-second life-or-death decisions
Much less complexity
Only ¼ the vehicle/vehicle conflict points; 1/3 ped/vehicle points
No right-turn, T-bone, head-on or red-light running crashes Much lower pedestrian exposure: distance, time, conflicts
Are Roundabouts Right for EMS and Public Health officials? Suitability Checklist Crashes -60% Injury crashes -76% Much lower crash energy Much less severe injuries Lethal crashes eliminated: head-on, T-bone, left-turning Fatalities virtually eliminated
Is Round Right for Evacuation Officials?
Maintenance. No sensors or electronics to fail
Roundabouts
• • None None
Signalized Intersections
• • Sensor loops Cabling & connections
• • Underground Overhead
• •
Controllers Signal heads
• • 8 heads 24 bulbs
• •
None None
Fail Safe
•
Electricity
• NO POWER NEEDED !!
Are Roundabouts Right for your Community?
Suitability Checklist Stakeholders throwing street parties, giving thumbs up Intersections friendly to kids, oldsters, handicapped persons and…cars Crashes way down, injuries way down, injury severity way down, fatalities eliminated Greenhouse gases way down Xtreme Benefit Cost Ratios AND compliment, reflect, enhance & celebrate the character, history, people and geology of the locale
Is Round Right for you??
Stakeholders throwing street parties, giving thumbs up Intersections friendly to kids, oldsters, handicapped persons and…cars Crashes way down, injuries way down, injuries severity way down, fatalities eliminated Greenhouse gases way down Xtreme Benefit Cost Ratios AND compliment, reflect, enhance & celebrate the character, history, people and geology of the locale