Progress withroundabouts

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Ourston Roundabout Engineering

Progress withProgress with Roundabouts to Date

Mark Lenters, President,

www.ourston.com1

Ourston Roundabout Engineering [email protected]

Progress by State

Ourston Roundabout Engineering www.ourston.com 2

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1990: The First U.S. Modern Roundabouts

Ourston Roundabout Engineering www.ourston.com

Town Center Drive, Summerlin, Nevada3

U.S. Since 1990

• 1990: Modern roundabouts built in Las Vegas.• 1995: UK style roundabouts replace signals &• 1995: UK style roundabouts replace signals &

create “Roundabout Valley” in Avon/Vail, CO.• 1997: HCM adds roundabouts• 2000 and 2010: FHWA Roundabouts: An

Informational Guide• 2010 HCM soon to be released


• US Currently building ~ 350 per year, and rising.

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National Collision Statistics

• Original 24 roundabouts before and after (c 2000)(c. 2000)

• Reduction in injuries = 76% • Combined reduction of all crashes = 40%

• Follow-up study combining results of 55 sites 1998 - 2003:


• 70% reduction in injuries• 35% reduction in all collisions combined• Similar to international statistics

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National collision statisticsfor multi-lane roundabouts

Intersection Type BeforeReduction in All Types

of Collisions withIntersection Type Before of Collisions with Roundabouts

Traffic Signals 67% All-Way Stop Control 12% Two-Way Stop Control Suburban 19%

Two-Way Stop Control 18%


Urban 18%

Note: Results based on a study of 26 multi-lane intersections converted to multi-lane roundabouts with 3 years of before and after data (source: NCHRP Report 572, 2006)

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Roundabout collisions = low severity (incorrect lane choice)


Roundabout collisions = low severity (failure to yield)


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Teaching drivers

at the..at the roundabout entry during opening



Roundabout SiteRoundabout Site Selection


www.ourston.com10


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Local and State Initiatives:Safet Impro ements

Identifying Candidate Intersections

• Safety Improvements• Congestion relief• Development permit

The Key mindset:


The Key mindset:- Be sure to solve a problem if a

roundabout is to be used!

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Selection process includes:

1. Initial planning level assessment performed as part of a study to evaluate the overall as pa o a s udy o e a ua e e o e aappropriateness of a roundabout;

2. Roundabout study considers site-specific conditions:• A safety assessment• Operational performance


• Cost comparison3. Requirements for drainage, lighting and

public outreach.

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1. Safety– Intersections with historically high crash rates.

Roads with a historical problem of excessive speeds

Locations where roundabouts are suitable:

– Roads with a historical problem of excessive speeds. – Intersections with more than four legs or with difficult skew

angles2. Operations

– A high % of turning movements and intersections that must accommodate U-turns.High traffic volumes at peak hours


– High traffic volumes at peak hours– Intersections where widening one or more approach may

be difficult or cost-prohibitive. – Ramp terminal intersections

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Cont’d…• Intersections with high traffic growth (A single-lane

d b t t d f i t t l )

Locations where roundabouts are suitable:

roundabout staged for expansion to two lanes)• Transitions between rural and urban - gateways 3. Traffic Control • Existing two-way stop-controlled intersections that do not

meet signal warrants. • Intersections or corridors where traffic calming is a


Intersections or corridors where traffic calming is a desired outcome of the project.

4. Aesthetics • Focal point for a community, gateway or themed

development

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Initial Screening ADT Thresholds


Typical Roundabout Capacity Ranges

Roundabout Type Typical Inscribed Circle Diameter1.

Typical Daily Service Volume2 (vpd)

4-leg roundaboutsMini-Roundabout 45-80 ft (14-28 m) Less than 30,000Urban Single-Lane 100 -150 ft (30 – 50 m) less than 25,000Urban Multilane

(2-lane entry) 160 - 215 ft (50 – 65 m) 25,000 to 55,000

Urban Multilane (3 or 4-lane

entry)215 - 275 ft (65 – 85 m) 55,000 to 80,000

Rural Single-Lane 130 -150 ft (35 – 55 m) less than 25,000

R l M ltil


Rural Multilane (2-lane entry) 165 - 215 ft (50 – 65 m) 25,000 to 55,000

Rural Multilane (3-lane entry) 215 – 300 ft (65 – 85 m) 55,000 to 70,000

1 Diameters are for general guidance.2Capacities vary depending on entering volume and turning / circulating flow.

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Conditions that may eliminate roundabout:

1. Coordinated signal system (platooned traffic)

2. R/W impacts3. Inadequate SSD4. Steep grades5. Minor improvement is that are more cost-

effective:


e ect e• No R/W required• Extend left turn bay• Add turn bay in existing median

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6. Intersections in close proximity to a signalized intersection (e.g., coordinated arterial signal systems)

Conditions that may eliminate roundabout:

7. Locations with steep grades and unfavorable topography that may limit visibility or an acceptable layout for a roundabout.

8. Intersections in close proximity to an at-grade railroad crossing.

9. Intersections where an unacceptable delay to the major


p y jroad could be created (90% main street traffic).

10.Heavy pedestrian or bicycle movements that may require signals.

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1. Project Background: describe site conditions2. Safety Assessment (historical crash data)

Intersection Control Study

y ( )3. Alternate Sketches – lane configuration, rough alignment4. Operational Analyses – Arcady, HCM5. Cost Comparison – Construction, crash savings, life-

cycle6. Alternative Selection – screening criteria (capacity,

safety cost)


safety, cost)7. Conceptual Roundabout Design – nearly a 30% design8. Conclusions and Recommendations

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Challenging but successful examples:- Railways- Railways- Corridors- Schools- Interchanges- Unusual geometry- Pedestrians

www.ourston.com

- Closely space intersections- Rural intersections- Access management

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Daingerfield, TX


Daingerfield, TX


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Corridor – Golden, CO

• 4 Signals changed to RBTS60% d i C h R t• 60% drop in Crash Rate

• 94% drop in injuries– From 31 in 3 yrs to only one:

a median opening left turn crash

• No Pedestrian crashes• No Pedestrian crashes• Single lane RBT has fewest

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Space and cost savings in a corridor...


Avon Colorado - Arterial Corridor, 1997

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Replaced traffic signalsat main intersection


Two decades of planned expansion


Second interchange for Wal-Mart in 2003

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Two interchanges in Vail, 1995


Interchange intersections previously controlled by police.

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Unusual Geometry

Avoided impacts to buildings & parking lots


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Pedestrian Signals At Roundabouts

Ourston Roundabout Engineering www.ourston.comwww.ourston.co29

Lee Rd @ Whitmore Lake Rd and US-23, Metro Detroit

Closely Spaced Intersections


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Rural High Speed Hwy. 85/Hwy. 17, 2006


Access Management

Loveland, CONarrow Median possibleb d b tbecause roundabouts

allow U-turns


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Rocky Mountain Avenue - 2008Business is still thriving


Lee Rd @ Whitmore Lake Rd and US-23, Metro Detroit

Closely Spaced Intersections


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Contiguous Roundabouts


Access Management

• Minor driveways can be designated as in intersection leg for access near entries or exits


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Transition Between Urban Forms(Clearwater Beach, FL)

Commercial with angle parking

r, FL


ResidentialResidential

Pho

to: C

ity o

f Cle

arw

ater

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J.F.K. Middle School, Clearwater, FL(>50 others like it in the U.S. being tracked)


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Non-Conforming Circle Becomes a Roundabout(Long Beach, CA, 1992)



Achieving SuccessAchieving Success Using Roundabouts


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• Lead with an Area-Wide Policy:

The Recipe for Successful Use of Roundabouts

– Roundabouts shall be considered when…– Conduct Alternatives Analyses (life cycle)– Top-down consensus building– Only use roundabouts to solve a problem


1.Assemble general policy tools2.Develop project specific tools

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General and Specific Outreach Tools

• Scale model• Case studiesGeneral Tools Project Specific Tools

• Animation/simulation• Renderings• Project web page• Project brochure

• Testimonials• National statistics• How-to videos• Web-cam• Driver training


• Driver training• Website• Brochures

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Scale Model (1:87 = ‘HO’ scale)


Coordination of Geometry and Lane Designation

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SB Pioneer Road Movement

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NB Belt Line Road Movement

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• Making Pedestrians more active…

Area-wide Education Campaigns


Documents

Progress withroundabouts