The Hilliard Triangle

1
The Hilliard Triangle

• Modern Roundabout
• Feasibility Study

2
Why Consider Modern Roundabouts?

• Reduces travel delay
• Greatly reduces severity of vehicle accidents
• Improves air quality
• Calms traffic
• Slows down traffic without increasing delay
• Proven solution
• Estimated

3
Other Advantages Of Roundabouts

• Aesthetic
• Landscaping
• Public art
• Generally no delay off-peak
• Community focal point
• Provides for greater visibility and easier access
  to nearby properties

4
Roundabout Concerns

• No traffic signal to assist pedestrians
• Blind pedestrians particularly challenged at
  roundabouts
• Requires more space at the intersection
• US drivers unfamiliar with modern roundabouts

5
Note On Safety

• Insurance Institute for Highway Safety reports
  that
• 39 decrease in crashes overall
• 76 decrease in injury accidents
• as much as 90 decrease in fatal or
  incapacitating injuries

6
Note On Safety (Cont)
Marylands Experience
7
Rules For Driving A Multi-Lane Roundabout

• On approach, a driver must choose the appropriate
  lane
• The right lane is used to make right turns or
  through
• The left lane is used to go through or make left
  turns and U-turns
• Once in the roundabout, the driver must not
  change lanes
• Drivers on the outside lane must yield to drivers
  exiting from the inside lane

8
Large Vehicles At Roundabouts

• Must straddle both lanes of two lane roundabout
• Cars must not try to pass trucks in roundabout
• Other vehicles should follow trucks into the
  roundabout
• Truck and bus drivers often prefer the large
  radius turn offered by roundabouts

9
Cautionary Note Regarding This Study

• Geometry still needs refinement
• Right-of-Way impacts may change
• Conceptual design-level of detail

10
Existing Site
11
Roundabout Alternatives Considered
B2
A1
C

• Requires 3-lane roundabouts (not recommended)
• Insufficient space for west roundabout (not
  recommended)

12
Roundabout Alternative
13
Signal Alternative
14
Level Of Service Comparison (Design Year 2025)
Unsignalized (HCS) Signalized (Synchro) Roundabout
(RODEL) Roundabout or Signal
15
Existing Right-Of-Way
Footprint Comparison
16
Right-Of-Way For Signal Alternative
Footprint Comparison
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Right-Of-Way For Roundabout Alternative
Footprint Comparison
18
Estimated Right-Of-Way Impacts
19
Travel Route Comparison
20
Travel Route Comparison
Non-Reciprocating Travel Routes
21
Travel Route Comparison
Non-Reciprocating Travel Routes
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Travel Route Comparison
Fully Reciprocating Travel Routes
23
Property Access Comparison

• Signal Alternative
• Access changed to right-in-right-out at driveways
  within left turn lane areas
• No U-turn opportunities
• Access on Scioto-Darby between Cemetery and Main
  is restricted by Turn Only intersections
• Roundabout Alternative
• All driveways accessible from any direction
• Right-in-right-out driveways have U-turn
  opportunities at the roundabouts
• Driveway locations shown may change

24
Pedestrians

• Roundabout Alternative
• Pros
• Low speed vehicle approach
• Vehicles approach from one direction per crossing
• Splitter island acts as refuge
• Peds cross maximum of 33 pavement
• Push button flashers can be added to increase
  driver awareness
• Cons
• Traffic does not stop
• Peds must judge vehicle gaps and speed
• Difficult for blind peds to cross

• Signal Alternative
• Pros
• Signal protected crossing
• Audible signal available to assist blind peds
• Cons
• Vehicles approach at high speeds
• Permitted right and left turn conflicts
• No pedestrian refuge
• Peds cross maximum 66 of pavement
• Traffic conflicts from multiple directions

25
Bicycles

• Roundabout Alternative
• Pros
• Low vehicle speeds easier for cyclists to match
• One-way traffic within roundabout
• Cons
• Best practice is for bicycles not to enter
  roundabout
• Cyclists should exit roadway and cross as
  pedestrians
• Drivers may not see cyclists easily

• Signal Alternative
• Pros
• Can share roadway with vehicles
• Signal operates same for bicycles as vehicles
• Cons
• Left turn must weave across through lanes
• High vehicle speeds through intersection

26
Construction Cost Comparison
1 Conceptual cost accuracy only. NOTE Other
undefined project costs include additional funds
for engineering, right-of-way acquisition, and
utility relocation.
27
Environmental / NEPA Considerations

• Project can be separated from Hilliard-Rome
  project
• Need to perform an environmental document
  re-evaluate (not a significant effort)
• Three different properties require Environmental
  Site Assessments
• No need to re-evaluate Cultural Resources
• No need to re-evaluate Ecological Resources
• Section 4(f) impacts involve a minor amount of
  additional acreage
• Noise will need to be re-analyzed to reflect
  redistribution of traffic
• One relocation likely is the former 76 service
  station, but not longer requiring a relocation of
  the insurance business at High School Drive
• New public involvement will be needed, however, a
  public education campaign will be required for
  the roundabouts in any event

28
Construction Phasing With Hilliard-Rome Project

• If roundabout alternative is to be constructed,
  it is beneficial to build after widening the Main
  Street section south of the Triangle
• Need to avoid construction back-ups into the
  roundabouts
• Expect one year to design and one to two years to
  acquire right-of-way
• FY2007 or FY2008 construction start

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Study Summary

• Signal Alternative
• Advantages
• Plans are 70 complete and nearly ready to
  acquire right-of-way
• Signalized intersection is familiar to drivers
• Satisfactory Level of Service in design year
• Provides safe pedestrian crossings at
  intersections
• Disadvantages
• Non-reciprocating travel paths
• Property access restrictions
• Places through traffic on High School Drive

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Study Summary (Cont)

• Roundabout Alternative
• Advantages
• Fully reciprocating travel paths
• Very high Level of Service in design year
• Provides greater vehicle safety
• Minimal access restrictions to properties
• U-turns allowable at roundabouts
• Disadvantages
• Pedestrian crossings a concern
• Requires two-phase signal at the west
  intersection to operate properly
• Drivers will be more confused initially
• Potential project delay
• Higher property impacts

31
Whats The Next Step?