FHWA Safety Performance for Intersection Control Evaluation (SPICE) ToolVirginia Section ITE Annual Meeting
Virginia Beach – June 2017
Pete Jenior
Kittelson & Associates, Inc.
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Intersection Control Evaluation (ICE) Background
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“DOTs should consider and evaluate [roundabouts, diverging diamond interchanges (DDIs) and intersections with displaced left-turns or variations on U-turns] early in the project scoping, planning and decision-making stages, as they may serve as more efficient, economical and safer solutions than traditional designs.”-FHWA
http://www.fhwa.dot.gov/everydaycounts/edctwo/2012/geometrics.cfm
States with objective intersection control evaluation policies:• California
• Indiana
• Minnesota
• Wisconsin
• Washington
• Under development:• Pennsylvania
• Florida
• Georgia
• Nevada
• Texas
Supported by FHWA’sEvery Day Counts Initiative• Shortening project delivery
• Enhancing roadway safety
• Protecting the environment
Intersection Control Evaluations
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What is an Intersection?
• The connection or crossing of two or more roadway facilities
Typical focus: At-grade forms
• We have been challenged implementing roundaboutsover the last 20 years
• We now have more “innovative” forms to consider
• Mostly treatments of left-turning vehicles
Intersection control evaluations apply to grade separated facilities
• Objective look at interchange form and function
• Focus is most often upon the ramp terminal intersection control of diamonds• Stop
• Yield (roundabout)
• Signalized – conventional
• Signalized – crossover (diverging diamond)
• Signalized – single intersection (single-point diamond)
Many Alternatives, Many Choices
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Perform engineering studies
Use appropriate analysis tools
Don’t disregard viable alternatives just because they are “new” or “different”
Source: NCHRP Report 825
VDOT ICE Efforts
VDOT Central Office developing screening tool
• Modification of FHWA CAP-X spreadsheet
• Critical lane volume analysis of alternative intersections
• Conflict point analysis
Additional tools/guidance/policy likely
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Intersection Control Evaluation General Steps
Consider project context
Initial screening evaluation
Performance-based decisions
• Operations
• Safety (the hard part!)
• Multimodal Quality Of Service
• Project Phasing
• Life Cycle Cost
Vision and Need for the SPICE Tool
Safety comparisons of intersections becoming more common – ICE, increased use of HSM in general, etc.
Challenges with safety analysis in early project stages
• Which CMF is “right”?
• What should the CMF be applied to(existing, another alt, etc.)?
• I heard there’s a new SPF for _____ - what is it?
Simple tool needed for intersection safety comparisons only
• Same level of effort as CAP-X
• Doesn’t need to do road segment safety
• Doesn’t need to do life cycle cost
• Doesn’t need to do delay, maintenance, emissions, etc.
• Established tools for these already
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Performs predictive safety analysis of at-grade intersection forms/control types and ramp terminal intersections
▪ Implements the methodologies of the Highway Safety Manual (HSM)
Developed with goal to be user-friendly
▪ Only requires data inputs readily available to the analyst
▪ Option to conduct planning level analysis
▪ Macro-powered Excel file
Allows simultaneous evaluation of multiple forms and control types
Tool will work for vast majority of intersections
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SPICE Tool Key Attributes
Predictive Safety Analysis of an Alternative
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Intersection Types
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At-Grade Intersections
• Traffic Signal (conventional)
• Minor-road Stop Control
• All-Way Stop
• Roundabout (yield control)
• Displaced Left Turn (DLT)
• Median U-Turn
• Signalized Restricted Crossing U-Turn (RCUT), also known Superstreet
• Unsignalized Restricted Crossing U-Turn (RCUT), also known as J-Turn
• Continuous Green-T Intersection
• Jughandles
Ramp Terminal Intersections of Diamond Interchanges
• Traffic Signal (conventional)
• Minor-road (i.e. ramp) Stop Control
• Roundabout (yield control)
• Single-point Traffic Signal (of a signal point diamond)
• Crossover Traffic Signal (of a diverging diamond)
At-Grade Intersections in SPICE Tool
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Control Facility Type # legs 1 way/ 2 way # of lanes on arterial
Traffic Signal On Rural Two Lane Highway 3 leg - -
4 leg - -
On Rural Multilane Highway 3 leg - -
4 leg - -
On Urban and Suburban Arterial 3 leg 2x2 5 or fewer
4 leg 2x2 5 or fewer
3 leg 2x2 6 or more
4 leg 2x2 6 or more
3 leg 1x2 -
4 leg 1x2 -
3 leg 1x1 -
4 leg 1x1 -
On High Speed (50+ MPH) Urban and Suburban Arterial 3 leg - -
4 leg - -
Minor Road Stop On Rural Two Lane Highway 3 leg - -
4 leg - -
On Rural Multilane Highway 3 leg - -
4 leg - -
On Urban and Suburban Arterial 3 leg 2x2 5 or fewer
4 leg 2x2 5 or fewer
3 leg 2x2 6 or more
4 leg 2x2 6 or more
3 leg 1x2 -
4 leg 1x2 -
3 leg 1x1 -
4 leg 1x1 -
On High Speed (50+ MPH) Urban and Suburban Arterial 3 leg - -
4 leg - -
All-Way Stop On Rural Two Lane Highway 4 leg - -
On Urban and Suburban Arterial 3 leg - -
On Urban and Suburban Arterial 4 leg - -
1-lane Roundabout - 3 leg - -
- 4 leg - -
2-lane Roundabout - 3 leg - -
- 4 leg - -
Displaced Left Turn (DLT) - - -
Median U-Turn (MUT) - - -
Signalized Restricted Crossing U-Turn (RCUT), also known Superstreet - - -
Unsignalized Restricted Crossing U-Turn (RCUT), also known as J-Turn - - -
Continuous Green-T Intersection - - -
Jughandles - - -
Ramp Terminal Intersections in SPICE Tool
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Control Ramp and Intersection Type
Conventional Traffic Signal Four-leg terminals with diagonal ramps (D4)
Crossover Traffic Signal (of Diverging Diamond Interchange) All types
Single-Point Diamond Traffic Signal All types
Minor Road (ramp) Stop Four-leg terminals with diagonal ramps (D4)
1-lane Roundabout 4 legs
2-lane Roundabout 4 legs
Alternative Intersections – what are they?
Median U-Turn (MUT)
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Alternative Intersections – what are they?
Restricted Crossing U-Turn (RCUT)
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Alternative Intersections – what are they?
Jughandle
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Alternative Intersections – what are they?
Displaced Left Turn
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Alternative Intersections – what are they?
Continuous Green T
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Alternative Intersections – what are they?
Quadrant Roadway
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Sources of Safety Information
HSM 1st Edition
CMF Clearinghouse
• Alternative intersections
NCHRP Project 17-58
• 6- and 8-lane urban and suburban arterial SPFs
• One-way urban and suburban arterial SPFs
NCHRP Project 17-70 (ongoing)
• Roundabout SPFs
NCHRP Project 17-68 (ongoing)
• 3-leg rural highway signal SPFs
• High-speed urban and suburban arterial SPFs
• All-way stop SPFs
• Single-point diamond SPFs
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Examples of Scenarios Accommodated by SPICE Tool
Primary Examples
• New intersection – conventional signal or various alternative forms
• Ramp terminal intersection with conventional signal, crossover signal (i.e. DDI), or roundabout
Secondary Examples
• TWSC being converted to signal or roundabout
• Signal being improved or converted to a roundabout
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SPICE – Introduction
Introduction
The Safety Performance for Intersection Control Evaluation (SPICE) Tool was developed to provide an
easy-to-use tool that automates the predictive safety analysis of intersections. This tool will allow
analysts conducting Intersection Control Evaluations (ICE) to be equipped with necessary safety
information during the decision-making process, without having to research a myriad of crash
modification factors (CMFs) and Safety Performance Functions (SPFs) in multiple sources. The SPICE
tool will perform a comparative predictive safety analysis of different intersection control strategies.
The results – crash frequency and severity for each alternative – will then enable safety performance
of alternatives to be considered quantitatively like traffic operations, construction cost, maintenance
cost, or other factors.
Maintenance
Version: SPICE Tool 1.0 Required data entry field
Maintained By: TBD Optional data entry field
Contact Information: TBD Planning-Level Default Input
Disclaimer Data entry field not used
Disclaimers may be added, if needed.
Input Legend
The SPICE Tool performs safety analysis of at-grade intersection forms/control types and ramp terminal
intersections of diamond interchanges. This user-friendly tool requires only data inputs that are readily
available to the analyst. In addition, the SPICE tool has an option to conduct planning level analysis,
where the tool assumes default values for data inputs that are challenging to obtain in the early stages
of a project and/or have a very minor impact on the results. The SPICE tool assumes that certain
attributes of the intersection – AADT, facility type, and number of legs – are the same for all alternatives.
If they are not, users will be required to use the tool twice to get results. The tool will not allow
simultaneous evaluation of at-grade intersections and ramp terminal intersections. For projects where
analysis of both intersections and interchanges is needed, users are required use the tool twice to get
results.
Federal Highway Administration (FHWA)
Safety Performance for Intersection Control Evaluation Tool
Overview
Project Information: Provide general project information for reference purposes only.
Worksheets
Alternative Selection: Specify the number of alternatives being considered and the intersection control of each alternative.
Predictive Inputs: Provide inputs needed to compute and apply Part C CMFs.
Calibration: Input optional override values for SPF calibration factors from locally-developed or updated information.
Results: Summary of opening year and (if applicable) design year and total project life cycle crash frequency and crash severity.
Additional Worksheets: Additional worksheets to support the underlying Macros. Not to be updated by users unless updating future tool versions.
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SPICE – Basic Inputs and Control Strategy Selection
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AADT Volumes for major/minor roads for the opening and design years
Number of major approaches with left-turn or right-turn lanes
Pre-filled planning-level defaults
▪ Can be overridden by analyst
SPICE – At-Grade Intersection Inputs
Opening Year Major Road AADT 20000
Opening Year Minor Road AADT 10000
Design Year Major Road AADT 25000
Design Year Minor Road AADT 15000
Number of Major (Uncontrolled) Approaches with Left-Turn Lanes
Number of Major (Uncontrolled) Approaches with Right-Turn Lanes
Skew Angle
Lighting Present
# of Approaches Permissive LT Signal Phasing
# of Approaches Perm/Prot LT Signal Phasing
# of Approaches Protected LT Signal Phasing
Number of Approaches with Right-Turn-on-Red Prohibited
Red Light Cameras Present
Number of Major Street Lanes (Including Turn Lanes)
Number of Minor Street Lanes (Including Turn Lanes)
# of Major St Approaches w/ Right-Turn Channelization
Number of Approaches with U-Turn Prohibited
Pedestrian Volume by Activity Level
User Specified Sum of all daily pedestrian crossing volumes
Max # of Lanes Crossed by Pedestrians
Number of Bus Stops within 1000' of Intersection
Schools within 1000' of intersection
Number of Alcohol Sales Establishments within 1000' of Intersection
Control Strategy
Planning Level Defaults (Optional Overrides)
Additional Required Control
Strategy Inputs
0
No
N/A
0
0
No
0
0
0
0
N/A
0
N/A
0
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5
N/A
N/A
N/A
InputBase
ConditionsMinor Road Stop
0
A yellow cell indicates the
value may be used in the SPF
computation
N/A
0
N/A
Yes
Optional
AADT
Overrides
20000
10000
25000
15000
Traffic Signal
20000
10000
25000
15000
0
0
0
0
0
Low (20)
No
0
Yes
N/A
Reset Planning Inputs to Defaults
Re
qu
ire
dO
ptio
na
l
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Crash Modification Factors (CMFs) used when safety performance functions (SPFs) are unavailable
CMFs can be overridden with local values
Local calibration factors can be applied when data is available
SPICE – CMF Specification and Optional Local Calibration
Default CMF
0.88
0.88
0.85
0.70
0.85
0.78
0.65
0.46
0.96
0.85
0.74
0.74
0.67
0.59
Optional - Override default CMFs with locallly-developed or new CMFs
Total
Total
Fatal-Injury
Total
Fatal-Injury
Fatal-Injury
Median U-Turn (MUT)
Signalized Restricted Crossing U-Turn (RCUT), also known Superstreet
Unsignalized Restricted Crossing U-Turn (RCUT), also known as J-Turn
Fatal-Injury
Continuous Green-T Intersection
Jughandles
Crossover Traffic Signal (of Diverging Diamond Interchange)
Total
Total
Total
Fatal-Injury
Fatal-Injury
Control
Displaced Left Turn (DLT)
Type of Crashes
Total
Fatal-Injury
Local CMFs
Use ValueOptional User
Override
0.74
0.74
0.67
0.88
0.88
0.85
0.70
0.85
0.59
0.85
0.78
0.65
0.46
0.96
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Control Strategy Crash Type Opening Year Design Year Total Project Life Cycle
Total 6.29 8.73 166.27
Fatal & Injury 2.55 3.57 67.72
Total 4.65 6.13 119.35
Fatal & Injury 2.23 3.01 57.94
Total 5.54 7.68 146.31
Fatal & Injury 2.24 3.14 59.59
Total 5.35 7.42 141.33
Fatal & Injury 1.78 2.50 47.40
Total 5.35 7.42 141.33
Fatal & Injury 1.99 2.79 52.82
Total 3.03 3.98 77.58
Fatal & Injury 1.02 1.38 26.65
Total 4.66 6.46 123.04
Fatal & Injury 1.89 2.64 50.11
Minor Road Stop
Crash Prediction Summary
Traffic Signal
Jughandle
Displaced Left Turn (DLT)
Median U-Turn (MUT)
Signalized RCUT
Unsignalized RCUT
Computes predicted crashes for all selected control strategy types
Predicted crashes are broken into “Total” and “Fatal & Injury” groups
SPICE – Crash Prediction Outputs
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Timeline and Questions
SPICE tool will be available in early 2018
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