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ROUNDABOUTS Improving Safety and Efficiency ROUNDABOUTS Improving Safety and Efficiency

ROUNDABOUTS Improving Safety and Efficiency - PowerPoint Presentation

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Uploaded On 2019-06-22

ROUNDABOUTS Improving Safety and Efficiency - PPT Presentation

The Ohio Department of Transportation District 3 906 Clark Ave Ashland OH 44805 Julie Cichello PE District Traffic Engineer Tel 4192077168 Email JulieCichellodotstateohus What is a roundabout ID: 759818

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Slide1

ROUNDABOUTS

Improving Safety and Efficiency

The Ohio Department of TransportationDistrict 3906 Clark Ave.Ashland, OH 44805

Julie Cichello, P.E.District Traffic EngineerTel: 419.207.7168Email: Julie.Cichello@dot.state.oh.us

Slide2

What is a roundabout?

A roundabout is a circular intersection in which traffic flows counterclockwise around a center island. There are no traffic signals or stop signs in a roundabout.

Slide3

Where are roundabouts appropriate?

High Crash Rate LocationsIntersection with Large Traffic DelaysComplex Geometry (i.e. more than four approaches)High Left Turn Volumes

Slide4

Key Roundabout characteristics

Circular in ShapeChannelized Approach (i.e. splitter island)Counterclockwise Traffic FlowYield Control on EntryGeometric Curvature Creates a Low Speed Environment

Right Turn in / Right Turn

out

Slide5

How to navigate a single Lane roundabout

Slow

Down!

20 mph or less is a safe entering speed.Yield!All entering vehicles must yield to circulating traffic in the roundabout.

Slide6

SINGLE LANE ROUNDABOUTS

Design Element

Single Lane RoundaboutMaximum Entry Design Speed20 to 25 mphMaximum Number of Entering Lanes per Approach1Typical Inscribed Circle Diameter90 to 180 ft.Center IslandRaisedDaily Service VolumeUp to 25,000 vehicles/day

Slide7

Design Element

Single Lane RoundaboutMaximum Entry Design Speed25 to 30 mphMaximum Number of Entering Lanes per Approach2+Typical Inscribed Circle Diameter150 to 300 ft.Center IslandRaisedDaily Service VolumeUp to 45,000 vehicles/day

MULTI-LANE ROUNDABOUTS

Multi-lane roundabouts are intended to accommodate higher volumes of traffic

Slide8

Benefits of roundabouts

Increased Traffic SafetyIncreased Pedestrian SafetyTraffic CalmingOperational PerformanceOngoing Operations and MaintenanceApproach Roadway WidthEnvironmental FactorsAestheticsLand Use

Slide9

THE FACTS89% Reduction in Fatalities76% Reduction in Injuries35% Reduction in Overall CrashesKey Message – Roundabouts are SAFER!

Traffic safety benefits

TYPICAL INTERSECTION vs. Roundabouts

Data from Federal Highway Administration’s website

Slide10

Traffic safety BENEFITSTYPICAL INTERSECTION vs. roundabouts

A typical 4-leg intersection contains 32 conflict points.A roundabout contains only 8 conflict points.All vehicles travel in the same direction, never crossing paths which dramatically reduces head-on and high speed angle crashes.

Converging (8)

Diverging (8)Crossing (16)

Converging (4)Diverging (4)Crossing (0)

Slide11

Angle and left turn crashes account for 63% of fatal crashes. A roundabout eliminates angle and left turn crashes by forcing vehicles to make a right turn in and out.Crashes that do occur in a roundabout are sideswipe in nature and less severe due to low vehicle speeds.

Traffic safety BENEFITS

TYPICAL Intersection vs. roundabouts

Slide12

SR 83 / Smithville Western Rd.

Crashes by Year

2009: 3

2010: 7

2011: 8

Slide13

Sr 83 / riffel road

Slide14

Benefits continued

Traffic CalmingRoundabouts have traffic calming effects by reducing vehicle speeds using geometric design. Operational PerformanceLess DelayRoundabouts typically have lower overall delay than signalized and all-way stop-controlled intersections. Delay reduction is most significant during non-peak traffic periods.  

Slide15

Benefits continued

Ongoing Operations and MaintenanceLower operating and maintenance costs than a traffic signal due to the lack of technical hardware, signal timing equipment, and electricity needs.Substantial cost savings to communities due to the reduction in crashes.Overall life cycle costs less than that of a signalized intersection. Approach Roadway WidthNo need for lengthy left or right turn lanes.

Slide16

Benefits continued

Environmental FactorsReduce the number and duration of stops compared with signalized or all-way stop-controlled alternatives. Reduction in noise and air quality impacts and fuel consumption by reducing the number of start/stops and the time spent idling. AestheticsLandscaping opportunities in the center island.“Gateway” into communities

Slide17

Public PERceptionBefore and after

NCHRP Synthesis 264

Slide18

ANY QUESTIONS?

Slide19

Sources

U.S. Dept. of Transportation. Federal Highway Administration. Office of Safety. Roundabouts. 2012. http://safety.fhwa.dot.gov/intersection/roundabouts/fhwasa10006/ppt/Washington State Dept. of Transportation. Roundabout Information. How to Drive a Roundabout. 2013. http://www.wsdot.wa.gov/safety/roundabouts/Wisconsin Dept. Of Transportation. Safety and Consumer Protection. Roundabouts. October 29, 2012. http://dot.wi.gov/safety/motorist/roaddesign/roundabouts/faq.htm