Module 8
Intersection & Interchange Geometrics (IIG)
Innovative Design Considerations for All Users
IntersectionInterchange
Evaluation
Process
INTERSECTION CONTROL EVALUATION
(ICE)
 Process to determine the “best” intersection design/traffic
control for a given location
 All alternatives are considered
 An evaluation of safety, operational, financial and political
impacts are compared
HISTORICAL “DEFAULTS”
 Almost all intersection “problems” are solved by installing a
traf fic signal
 Traffic Signal Warrants/Justification
 Separate process for other alternatives
 Historical default is to only consider traditional
countermeaures
 traffic signal
 all way stop
ICE PROCESS
 All alternatives are considered
 Initial screening for feasibility
 Technical Analysis
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Safety
Capacity/Operations
Costs – Benefit Costs
Right of Way impacts
 Public/Political Considerations
 Selection of preferred alternative
 “Best” alternative
 Documented in report
 Subject to available funding, other projects, project readiness, etc
BENEFITS OF ICE
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Quantification of “Best” alternative
Decision is documented
Potential for better decision making
Important Criteria are analyzed
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Safety (quantitative)
Capacity (quantitative)
Construction, ROW and Maintenance Costs (quantitative)
Political and Public acceptability (qualitative)
MINNESOTA ICE
 Developed in 2007 with the desire to include roundabouts as
an alternative to traf fic signals
 Safety and Capacity Analysis is required using acceptable
methods
 Report documenting findings and recommendations must be
submitted and approved by the District Traf fic Engineer
http://www.dot.state.mn.us/trafficeng/safety/ice/
index.html
WISCONSIN
 Facilities Development Manual
 11-25-3 Intersection Control Evaluation
 ICE Worksheet
 Documents the technical and financial analysis of alternatives
 Project using Federal or State funding must complete the
worksheet
 Two Phases (Scoping/Alternative Selection
 Decision is documented
INDIANA
Intersection Design Guide (2013)
First a “need” must be determined to evaluate solutions to
All alternatives are considered, including “no build”
Decision Trees help determine feasibility, eliminate
alternatives
 Safety, Capacity and Costs are all considered as well as other
factors
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CALIFORNIA
 Traffic Operations Policy Directive (2013)
 Updates evaluation procedures for
determining ef fective traf fic control
strategies for subject intersection
 Assessment Phase – Identification of
one or more strategies that will meet the
“need” for control
 Engineering Analysis – Safety, Capacity
and Life-Cycle Costs
 Establishment of District ICE
coordinators
 All users are considered
CALIFORNIA
http://dot.ca.gov/hq/traffops/liaisons/ice.html
SIX STEP METHODOLOGY
Ch 10 Alternative Intersection
Assessment
FITS WITHIN EXISTING PROJECT
DEVELOPMENT PROCESS
• The needs identified in prior planning studies should “inform” (not dictate)
the identification, development, and evaluation of intersection control and
geometry concepts.
• It is critical to understand the project context and intended outcomes prior
to developing potential solutions so that options may be tailored to meet
project needs within the opportunities and constraints of a given effort.
Step 1 – Establish Objectives
 Having a clear understanding of the purpose and need is a
fundamental step in evaluating alternatives
“ Why are we building this project?”
 Stakeholder outreach is critical to developing meaningful
and appropriate objectives
 Project goals and objectives (i.e. performance
characteristics) should be specific, they should be
measurable and directly relate to the purpose and needs
Step 2 – Multi-modal User Assessment
When considering intersection alternatives, integrate pedestrian, bicycle,
and transit needs at an early stage of the project planning process. The
unique characteristics of intersection options produce variations in the
physical geometry and traffic control schemes which can introduce both
benefits and challenges to pedestrians, bicyclists and transit users.
Step 3 – ROW & Context Assessment
• Assess the overall corridor (or isolated intersection) context including the built,
natural, and community environment and the intended performance outcomes
of the intersection form
• Document the intended context, and how operations, safety, and geometry fit
the context for each alternative including intended users (pedestrians,
bicyclists, passenger cars, transit vehicles, freight, emergency responders, and
over size/over weight vehicles)
• Compare the ROW needs and economic impacts of practical alternatives
Step 4 – Access Management
Assessment
Access management considerations:
• Driveway spacing
• Adjacent signal spacing
• U-Turns
STEP 5 – SKETCH LEVEL TRAFFIC
ANALYSIS
OPERATIONAL ANALYSIS TOOL OVERVIEW
• Planning-level analysis, such as critical lane volume and Capacity Analysis for
Planning of Junctions (CAP-X)
• Highway Capacity Manual (HCM) Analysis
• Microsimulation analysis
Step 5 – Sketch Level Traffic Analysis
CAP-X SPREADSHEET
Step 6 – Detailed Traffic Analysis of
Viable Alternatives
Detailed traffic simulation analysis of
the most promising alternatives
QUALIT Y OF SERVICE
Quality of service is defined as the perceived quality of travel by a road user. It is used
in the 2010 HCM to assess multimodal level of service (MMLOS) for motorists,
pedestrians, bicyclists, and transit riders.
Quality of service may also include the perceived quality of travel by design
vehicle users such as truck or bus drivers.
INTERPRETING RESULTS
Alt A
Alt B
i.e. Intersection Delay
Performance Measure
Hypothetical Cost-Effectiveness Graph of Four Alternatives
Alt G
Minimum Desirable LOS
Alt R
Cost
QUESTIONS