Progress withroundabouts

Ourston Roundabout Engineering

Progress with
Roundabouts to Date
Mark Lenters, President,
Ourston Roundabout Engineering Inc.
mlenters@ourston.com

www.ourston.com
1

Progress by State

Ourston Roundabout Engineering www.ourston.com 2

1

1990: The First U.S. Modern
Roundabouts

Town Center Drive, Summerlin, Nevada

U.S. Since 1990
• 1990: Modern roundabouts built in Las Vegas.
• 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.


2

National Collision Statistics

• Original 24 roundabouts before and after
(c.
(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


National collision statistics
for multi-lane roundabouts
Reduction in All Types
Intersection Type Before of Collisions with
Roundabouts
Traffic Signals 67%
All-Way Stop Control 12%
Two-Way Stop Control
19%
Suburban
Two-Way Stop Control
18%
Urban
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)


3

Roundabout collisions =
low severity (incorrect lane choice)


Roundabout collisions =
low severity (failure to yield)


4

Teaching drivers

..at the
at
roundabout
entry during
opening



Roundabout Site
Selection

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5

Identifying Candidate
Intersections
Local and State Initiatives:
• Safet Improvements
Safety Impro ements
• Congestion relief
• Development permit

The Key mindset:
- Be sure to solve a problem if a
roundabout is to be used!


Selection process includes:
1. Initial planning level assessment performed
as pa o a s udy to e a ua e the o e a
part of study o evaluate e overall
appropriateness of a roundabout;
2. Roundabout study considers site-specific
conditions:
• A safety assessment
• Operational performance
• Cost comparison
3. Requirements for drainage, lighting and
public outreach.


6

Locations where roundabouts are
suitable:
1. Safety
– Intersections with historically high crash rates.
– Roads with a historical problem of excessive speeds
speeds.
– Intersections with more than four legs or with difficult skew
angles
2. Operations
– A high % of turning movements and intersections that
must accommodate U-turns.
– High traffic volumes at peak hours
– Intersections where widening one or more approach may
be difficult or cost-prohibitive.
– Ramp terminal intersections


Locations where roundabouts are
suitable:
Cont’d…
• Intersections with high traffic growth (A single-lane
roundabout staged f expansion t two lanes)
d b t t d for i to t l )
• 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
desired outcome of the project.
4. Aesthetics
• Focal point for a community, gateway or themed
development

7

Initial Screening ADT Thresholds


Typical Roundabout Capacity Ranges
Typical Daily Service
Typical Inscribed Circle
Roundabout Type Volume2 (vpd)
Diameter1.
4-leg roundabouts
Mini-Roundabout 45-80 ft (14-28 m) Less than 30,000
Urban Single-Lane 100 -150 ft (30 – 50 m) less than 25,000
Urban Multilane
160 - 215 ft (50 – 65 m) 25,000 to 55,000
(2-lane entry)
Urban Multilane
(3 or 4-lane 215 - 275 ft (65 – 85 m) 55,000 to 80,000
entry)
Rural Single-Lane 130 -150 ft (35 – 55 m) less than 25,000
Rural M ltil
R l Multilane
165 - 215 ft (50 – 65 m) 25,000 to 55,000
(2-lane entry)
Rural Multilane
215 – 300 ft (65 – 85 m) 55,000 to 70,000
(3-lane entry)
1 Diameters are for general guidance.
2Capacities vary depending on entering volume and turning / circulating flow.


8

Conditions that may eliminate
roundabout:
1. Coordinated signal system (platooned
traffic)
2. R/W impacts
3. Inadequate SSD
4. Steep grades
5. Minor improvement is that are more cost-
e ect e
effective:
• No R/W required
• Extend left turn bay
• Add turn bay in existing median


Conditions that may eliminate
roundabout:
6. Intersections in close proximity to a signalized
intersection (e.g., coordinated arterial signal systems)
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 j
road could be created (90% main street traffic).
10. Heavy pedestrian or bicycle movements that may
require signals.


9

Intersection Control Study
1. Project Background: describe site conditions
2. Safety Assessment (historical crash data)
y ( )
3. Alternate Sketches – lane configuration, rough alignment
4. Operational Analyses – Arcady, HCM
5. Cost Comparison – Construction, crash savings, life-
cycle
6. Alternative Selection – screening criteria (capacity,
safety,
safety cost)
7. Conceptual Roundabout Design – nearly a 30% design
8. Conclusions and Recommendations



Challenging but successful examples:
- Railways
- Corridors
- Schools
- Interchanges
- Unusual geometry
- Pedestrians
- Closely space intersections
- Rural intersections
- Access management

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10

Daingerfield, TX


Daingerfield, TX


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Corridor – Golden, CO

• 4 Signals changed to RBTS
• 60% ddrop i C h R t
in Crash Rate
• 94% drop in injuries
– From 31 in 3 yrs to only one:
a median opening left turn
crash
• No Pedestrian crashes
• Single lane RBT has fewest

23

Space and cost savings in
a corridor...

Avon Colorado - Arterial Corridor, 1997


12

Replaced traffic signals
at main intersection


Two decades of planned expansion

Second interchange for Wal-Mart in 2003


13

Two interchanges in Vail, 1995

Interchange intersections previously controlled by police.


Unusual Geometry
Avoided impacts to
buildings & parking lots


14

Pedestrian Signals At
Roundabouts

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


15

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


Access Management
Loveland, CO
Narrow Median possible
because roundabouts
b d b t
allow U-turns


16

Rocky Mountain Avenue - 2008
Business is still thriving


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


17

Contiguous Roundabouts


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


18

Transition Between Urban Forms
(Clearwater Beach, FL)

Commercial with
angle parking

Photo: City of Clearwater FL
r,
Residential


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


19

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



Achieving Success
Using Roundabouts

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20

The Recipe for Successful Use of
Roundabouts
• Lead with an Area-Wide Policy:
– 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 tools
2.Develop project specific tools


General and Specific Outreach Tools
General Tools Project Specific Tools
• Case studies • Scale model
• Testimonials • Animation/simulation
• National statistics • Renderings
• How-to videos • Project web page
• Web-cam • Project brochure
• Driver training
• Website
• Brochures


21

Scale Model (1:87 = ‘HO’ scale)


Coordination of Geometry and
Lane Designation

44

22

SB Pioneer Road Movement

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NB Belt Line Road Movement

Ourston Roundabout Engineering 46 www.ourston.com

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Area-wide Education Campaigns

• Making Pedestrians more active…


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