intersection & interchange geometrics (iig) innovative design considerations for all users...
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Intersection & Interchange Geometrics (IIG)Innovative Design Considerations for All Users
Module 8
Intersection-Interchange Evaluation Process
INTERSECTION CONTROL EVALUATION (ICE)
Process to determine the “best” intersection design/traffi c control for a given location
All alternatives are consideredAn evaluation of safety, operational, financial and
political impacts are compared
HISTORICAL “DEFAULTS”
Almost all intersection “problems” are solved by installing a traffi c signal
Traffi c Signal Warrants/JustificationSeparate process for other alternativesHistorical default is to only consider traditional
countermeaures traffi c signal all way stop
ICE PROCESS
All alternatives are considered Initial screening for feasibilityTechnical Analysis
Safety Capacity/Operations Costs – Benefit Costs Right of Way impacts
Public/Political ConsiderationsSelection of preferred alternative
“Best” alternative Documented in report Subject to available funding, other projects, project
readiness, etc
BENEFITS OF ICE
Quantification of “Best” alternativeDecision is documentedPotential for better decision making Important Criteria are analyzed
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 traffi c signals
Safety and Capacity Analysis is required using acceptable methods
Report documenting findings and recommendations must be submitted and approved by the District Traffi c 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
alternativesProject using Federal or State funding must
complete the worksheetTwo Phases (Scoping/Alternative SelectionDecision is documented
INDIANA
Intersection Design Guide (2013)First a “need” must be determined to evaluate
solutions toAll alternatives are considered, including “no build”Decision Trees help determine feasibility, eliminate
alternativesSafety, Capacity and Costs are all considered as well
as other factors
CALIFORNIA
Traffi c Operations Policy Directive (2013)
Updates evaluation procedures for determining eff ective traffi c 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
http://dot.ca.gov/hq/traffops/liaisons/ice.html
CALIFORNIA
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 specifi c, they should be measurable and directly relate to the purpose and needs
Step 2 – Multi-modal User AssessmentWhen 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
QUALITY 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 designvehicle users such as truck or bus drivers.
INTERPRETING RESULTS
Hypothetical Cost-Effectiveness Graph of Four Alternatives
Cost
Perf
orm
an
ce
Measu
rei.e.
Inte
rsect
ion D
ela
y
Minimum Desirable LOS
Alt A
Alt G
Alt R
Alt B
QUESTIONS