Post on 07-May-2015
description
VirginiaStatewide Roundabout Guidance
TRB 4th International Conference on RoundaboutsApril 17, 2014
Andy Boenau
Chris Tiesler
VirginiaAndy Boenau
1.BackgroundPart
Statewide Roundabout Guidance
Option A = familiar throughout the U.S.; lots of death & destruction
Option B = familiar throughout the world; lots of life & prosperity
Intersection Design Options
“We connect land use
(said every DOT everywhere)
and transportation.”
Virginia DOT Transportation & Land Use Publications
“ensuring the
connectivity of pedestrian
networks”
“fundamental modes”
“enhance quality”
“…[roundabout] should be consideredthe Department’s
preferred alternative…”
Virginia Policy
If feasible, then preferred.
Why?
If feasible, then preferred.
Why?
Because we want more people to live!
Since single-lane roundabouts are thesafest form of at-grade intersection,
for pedestrians, bicyclists, and motorists!why aren’t there more
in Virginia?
Institutional bias
stat
e ag
enci
es
polit
icia
nsneighbors
consultants
and the fear of change.
Illustration of the anti-roundabout bias…
Roundabout1.Yield to traffic already in roundabout.
Traffic Signal1. 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
c) you may go straight or turn right
d) 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 cannotb) 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
A motorist has to make a lot of decisions
Roundabouts are simple.
before driving through a traffic signal...even when they aren’t fatigued or distracted.
If the general public trusts us
[deadly] status quo?
to design safe infrastructure, can wemake progress by following the
Transportation engineers now havea much broader perspective about
the purpose and use of streets.
Complete street
Tactical urbanismWalk to school
Arts district
Crosswalks
Bus shelters
Traffic calming
Livable streetEconomic development
Bike to schoolLess parking
Separated bike paths
Road diet
Placemaking
We have the engineering knowledge base.
We have a strong roundabout policy.
So how do we buildmore roundabouts in Virginia?
2.Process + ToolsPart
VirginiaChris Tiesler
Statewide Roundabout Guidance
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
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
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
AAD
T
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)
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)
Roundabout C onfiguration Typical Design
Vehicle C ommon Inscribed C ircle
Diameter Range*
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.
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)
140’ ICD
Planning-Level Screening
Network Interactions Consider site and surround intersection(s) in close proximity
Intersection spacing?Adjacent traffic control – related queuing characteristicsCorridor 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)
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
Key Takeaways
Easy to use
Requires basic information that is readily available
Evaluate criteria beyond traffic operations
BETTER DECISIONS
What do I need?
Opening year and design year ADTsRecent turning movement countsOperational 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
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
MainENTRY Tab
User-friendly drop list fields allow for easy scenario selection
Non-applicable fields blocked out in gray
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
AdjustSPF Tab
Data entered uses HSM Part C CMFs to complete the SPF calculations
Only fields for selected facility type are shown
DelayENTRY Tab
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
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
Tool #3: Design Guidance Document
Condensed design guidance for practitionersEmphasize 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
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
TRB 4th International Conference on Roundabouts April 17, 2014
Be socialwith us
during#Rndbt2014