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The Virginia Department of Transportation (VDOT) revised its Road Design Manual in 2008 to include a policy statement on roundabouts. The policy says that “[...when a roundabout is feasible] it should be considered the Department’s preferred alternative due to the proven substantial safety and operational benefits. This is one of the stronger policy statements of any state in the United States. However, it has been difficult for VDOT to consistently implement and adhere to this policy on intersection projects throughout the state without a supporting process and/or tool and appropriate guidance. Timmons Group and Kittelson & Associates, Inc. were hired to develop a repeatable process and series of tools to quickly and efficiently evaluate roundabouts. The intent was to create a procedure that could be used early in project planning and continue through project design. This presentation was given by Chris Tiesler and Andy Boenau during the 62nd Annual Meeting of the Southern District Institute of Transportation Engineers.
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Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Statewide Roundabout Guidance
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Andy Boenau
Chris Tiesler
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Andy Boenau
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
1. Background
Part
Statewide Roundabout Guidance
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Option A = familiar throughout the U.S.;
lots of death & destruction
Option B = familiar throughout the world;
lots of life & prosperity
Intersection Design Options
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
“We connect land use
(said every DOT everywhere)
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Virginia DOT Transportation & Land Use Publications
“fundamental modes”
“enhance quality”
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
“…[roundabout] should be considered the Department’s
preferred alternative…”
Virginia Policy
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
If feasible, then preferred.
Why?
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
If feasible, then preferred.
Why?
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Since single-lane roundabouts are the safest form of at-grade intersection,
why aren’t there more in Virginia?
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Institutional bias
and the fear of change.
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Roundabout
1.Yield to traffic already in roundabout.
Rules of the road
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Traffic Signal 1. If the signal is a red ball, come to a complete stop
a) After stopping, you may turn right but must yield to oncoming traffic; except if the sign says "NO TURN ON RED", you cannot
b) After stopping, you may turn left on red from a one-way street onto a one-way street but must yield to oncoming traffic
2. If the signal is a green ball
a) you may go straight or turn right, but only if the way is clear - you must yield to vehicles still in the intersection
b) you may turn left but must yield to oncoming traffic
3. If the signal is a yellow ball
a) you may go straight or turn right
b) you may turn left but must yield to oncoming traffic
4. If there is one signal head for several lanes, it applies to all those lanes; if there is a signal head for each lane, each lane is governed by its own signal head; and if
there are multiple heads but not as many as there are lanes, generally a head centered above a lane governs that lane, a single head located above the line dividing
two lanes governs both lanes, and a single head centered above three lanes governs all three lanes
5. If the signal for your lane is a red arrow pointing left or right, come to a complete stop
a) After stopping, you may turn right on red but must yield to oncoming traffic; except if the sign says "NO TURN ON RED", you cannot
b) After stopping, you may turn left from a one-way street onto a one-way street ; except if the sign says "NO TURN ON RED", you cannot
6. If the signal for your lane is a red arrow pointing up, you may not go straight
7. If the signal for your lane is a green arrow pointing left or right, you may turn in the direction of the arrow, after yielding the right-of-way to vehicles within the
intersection, even if the red light is burning at the same time
8. If the signal for your lane is a green arrow pointing up, you may go straight, after yielding the right-of-way to vehicles within the intersection, even if the red light is
burning at the same time
9. If the signal for your lane is a yellow arrow, it means the same thing as the yellow ball, but applies only to movement in the direction of the arrow
10. If the signal is a blinking red ball, come to a complete stop and then enter the intersection, except you must yield to other vehicles already in the intersection
11. If the signal is a blinking yellow ball, enter the intersection with caution, except you must yield to other vehicles already in the intersection
12. If none of the bulbs on the signal head are illuminated (power outage), come to a complete stop and then enter the intersection with caution, except you must
yield to other vehicles already in the intersection
*special thanks to Ken Sides
Rules of the road
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
A motorist has to make a lot of decisions
If the general public trusts us
[deadly] status quo?
before driving through a traffic signal... even when they aren’t fatigued or distracted.
to design safe infrastructure, can we make progress by following the
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Transportation engineers now have a much broader perspective about
the purpose and use of streets.
Complete street
Tactical urbanism Walk to school
Arts district
Crosswalks
Bus shelters
Traffic calming
Livable street Economic development
Bike to school Less parking
Separated bike paths
Road diet
Placemaking
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
We have the engineering knowledge base.
We have a strong roundabout policy.
So how do we build more roundabouts in Virginia?
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
2. Process + Tools
Part
Chris Tiesler
Statewide Roundabout Guidance
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Background
State agencies with successful roundabout programs generally have
Policy statement
Process
Internally apply the intent of the policy
Tools
Assist in performing assessments
VDOT has a strong policy, but has lacked a process and tools to consistently implement and adhere to its policy
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Three Tools
Screening Guidance Planning-level feasibility
Spreadsheet Tool Compare control forms
Go beyond operations
Easy to use/maintain
User Manual companion
Design Guidance Principle-based
Resource
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Tool #1: Planning-Level Screening Document
Determine General Lane Needs
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
0
5,000
10,000
15,000
20,000
25,000
30,000
35,000
40,000
45,000
50,000
0% 10% 20% 30% 40%
Left-Turn Percentage
AA
DT
Double-lane roundabout
likely to operate acceptably
Single-lane roundabout may be
sufficient (additional analysis needed)
Single-lane roundabout
likely to operate acceptably
Double-lane roundabout may be
sufficient (additional analysis needed)
Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Planning-Level Screening
Right of Way Determine approximate footprint
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
Adapted from NCHRP Report 672 (Exhibit 6-9)
Rounda b out C onfigura tion
Typ ic a l D e s ig n
Ve h ic le
C om m on Ins c rib e d C irc le
D ia m e te r Ra nge *
Mini-Roundabout SU-30
45 to 90 ft
Single-Lane Roundabout B-40 90 to 150 ft WB-50 105 to 150 ft WB-67
130 to 180 ft
Multilane Roundabout (2 lanes) WB-50 150 to 220 ft WB-67
165 to 220 ft
Multilane Roundabout (3 lanes) WB-50 200 to 250 ft WB-67
220 to 300 ft
* Assumes 90-degree angles between entries and no more than four legs. List of possible design vehicles not all-inclusive.
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Planning-Level Screening
Approximate magnitude/size of roundabout and associated impacts can be initially judged
Consider: Right of way
Environmental impacts
Utilities
Topography
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Planning-Level Screening
Network Interactions Consider site and surround intersection(s) in close proximity
Intersection spacing?
Adjacent traffic control – related queuing characteristics
Corridor considerations
Roundabouts particularly desirable when: Low percentage of through trips and high percentage of turns
Safety improvements desirable
Community enhancement/aesthetics
Traffic calming
High number of U-turns
Unusual geometry creates design and signal phasing challenges
Figure 1 – Planning Level Daily Intersection Volumes (NCHRP Report 672 Exhibit 3-12)
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Tool #2: Spreadsheet Tool
Compares life-cycle costs of roundabout to traffic signal or stop-control across range of criteria
Elements included: Safety
Vehicular delay
Operations and Maintenance
Capital design and construction costs
Right-of-way cost
Elements not included: Emissions and fuel consumption
Other qualitative elements
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Key Takeaways
Easy to use
Requires basic information that is readily available
Evaluate criteria beyond traffic operations
BETTER DECISIONS
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
What do I need?
Opening year and design year ADTs
Recent turning movement counts
Operational analysis to determine: Turn lane requirements
Control delay
Basic geometric layout
Historical crash data (optional)
Preliminary cost estimate
User is prompted for additional detail as needed (case-by-case) Assumptions can be made
Straightforward inputs
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Introduction Tab
Provides spreadsheet navigation instructions
Color Coding Orange cells indicate required
data entry
Blue cells indicate optional data entry
Red text provides further instruction
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
MainENTRY Tab
User-friendly drop list fields allow for easy scenario selection
Non-applicable fields blocked out in gray
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Highway Safety Manual Content
Part C – Predictive Method
10: Two-Lane Rural Highways
11: Multilane Rural Highways
12: Urban and Suburban Arterials
Part D – Crash Modification Factors
13: Roadway Segments
14: Intersections
15: Interchanges
16: Special Facilities
17: Networks
Glossary
Part A – Introduction and Fundamentals
1: Introduction
2: Human Factors
3: Fundamentals
Part B – Roadway Safety Management
4: Network Screening
5: Diagnosis
6: Select Countermeasures
7: Economic Evaluation
8: Prioritization
9: Safety Effectiveness Evaluation
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
AdjustSPF Tab
Data entered uses HSM Part C CMFs to complete the SPF calculations
Only fields for selected facility type are shown
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
DelayENTRY Tab
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
VDOT Spreadsheet Tool - Results
Calculates the monetary
safety and delay benefit of
the roundabout
Compares to ops/maintenance
and initial capital costs
expenditures
Life Cycle Benefit/Cost Ratio
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Spreadsheet Tool Summary
Spreadsheet tool compares intersection control forms across wide range of criteria Operations
Safety
Costs Construction
Operations/Maintenance (Life Cycle)
Easy to use and maintain
Supplements initial roundabout screening tool
User Manual provides detailed information regarding methodologies
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Tool #3: Design Guidance Document
Condensed design guidance for practitioners
Emphasize key principles Planning
Economic Evaluation
Public Involvement
Operations
Safety
Design Design Vehicle
Splitter Islands
Truck Apron
Non-motorized Users
Curbs/Drainage
Traffic Control Devices
Illumination
Landscaping
Southern District Institute of Transportation Engineers 62nd Annual Meeting March 31, 2014
Next Steps
Roll out tentatively planned for July 2014 to coincide with update to VDOT Road Design Manual
All three tools likely to be housed and available on VDOT’s external Roundabouts website http://www.virginiadot.org/info/faq-roundabouts.asp
Education & training for VDOT staff and consultant community
Andy @Boenau
@timmonsgroup
Chris @ctiesler
@kittelson
Southern District Institute of Transportation Engineers
62nd Annual Meeting
March 31, 2014
Be social with us
during
#SDITE2014
