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

20

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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