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TRANSCRIPT
Seyedehsan (Ehsan) Dadvar, PhD, RSP1
NRC Fellow at FHWA
Lifesavers 2020 Conference
March 16th, 2020
Tampa, FL
How can the Highway Safety Manual
(HSM) and associated tools save lives?
Source: FHWA
Source: FHWASource: AASHTO
Workshop: Innovative Engineering to Protect All Road Users
Outline
● Introduction
● Highway Safety Manual (HSM)○ Overview
○ Forthcoming 2nd Edition
● Interactive Highway Safety Design Model (IHSDM)○ Overview
○ Case Studies
● Crash Modification Factor (CMF) Clearinghouse○ Overview
○ New feature in IHSDM (Ver. 15.0.0): “User-defined CMFs”
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Road Safety in the US
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Road safety in the US (Cont.)
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NY-30A & NY-30, Schoharie, NY 12157
Schoharie Limousine Crash (October 6th, 2018)
The deadliest road crash since 2005
20 people killed:
● Driver and 17 passengers of a limousine
● Two pedestrians in parking lot
Road Safety in the News
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Road Safety in Research
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Highway Safety Manual (HSM)
● The 1st edition published: 2010○ New chapters on freeways & ramps were released in 2014
● Methodology is like that for assessing and assuring
the adequacy of capacity
● HSM allows the transportation professionals to
understand and quantify highway safety performance
for informed and balanced decision making;
however, does not replace design manuals.
● “[T]he HSM is written for practitioners at the state,
county, metropolitan planning organization (MPO), or
local level (HSM, Page 1-1).”
7www.highwaysafetymanual.org
(Cont.)
Objective
● Reduce the number / severity of crashes within the limits of available
resources, science, technology, and priorities
Application
● Identify facilities with the greatest potential for safety improvement
● Compare different design options
● Assess the safety “benefits” when conducting a B/C analysis
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Source: FHWA
(Cont.)
Application: Same traffic volume, two alternatives vs. No-Build!
The HSM can be used in conjunction with Road Safety Audits (RSA).
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(Cont.)
HSM four parts:
● Part A — Introduction, Human Factors, and Fundamentals
● Part B — Roadway Safety Management Process
● Part C — Predictive Method
● Part D — Crash Modification Factors
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❖ Network Screening
❖ Diagnosis
❖ Select Countermeasures
❖ Economic Appraisal
❖ Prioritize Projects
❖ Safety Effectiveness Evaluation
CRSMS Tool for ConnDOT
(Cont.)
HSM four parts:
● Part A — Introduction, Human Factors, and Fundamentals
● Part B — Roadway Safety Management Process
● Part C — Predictive Method
● Part D — Crash Modification Factors
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❖ Rural Two-lane Roads
❖ Rural Multi-lane Highways
❖ Urban / Suburban Arterial Highways
❖ Freeway Segments & Speed-Change Lanes
❖ Ramps, C-D Roads, & Ramp-Terminals
HSM Spreadsheet Tools
(including ISATe)
(Cont.)
HSM four parts:
● Part A — Introduction, Human Factors, and Fundamentals
● Part B — Roadway Safety Management Process
● Part C — Predictive Method
● Part D — Crash Modification Factors
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421 CMFs
❖ Roadway Segments
❖ Intersections
❖ Interchanges
❖ Special Facilities and
Geometric Situations
❖ Road Networks
(Cont.)
● Safety performance of different facility types investigated:○ Roadway segments, Intersections / Interchanges
○ Rural, Urban & Suburban
● Safety impact of different factors examined:○ Lighting
○ Horizontal Curvature (e.g., radius)
○ Lane Width
○ Automated Speed Enforcement
○ Median Width
○ Right / Left Shoulder Width
○ Left / Right Side Barrier
○ Driveways
○ Roadside Fixed Objects
○ etc.13
(Cont.)
● The 2nd edition of the HSM is under development.
● Revised chapters and improved content (e.g., expanded human factors)
● More facility types:
○ More intersection types (e.g., roundabouts)
○ More roadway segment types (e.g., one-way highways)
● Improved approach of predicting crashes involving pedestrians / bicyclists
● Improved transfer / calibration approach to apply models to local conditions
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Interactive Highway Safety Design Model (IHSDM)
● A “free-of-charge” product of FHWA’s Safety Research and Development
Program: Geometric Design Laboratory (GDL)
● A suite of software tools that support project-level geometric design decisions
● Provides quantitative information on the expected safety and operational
performance
● IHSDM results help project developers make design decisions that improve
the expected safety performance
● IHSDM helps project planners, designers, and reviewers justify and defend
geometric design decisions (e.g., RSAs)
15www.ihsdm.org
● Crash Prediction Module (CPM) ⇒ Faithful implementation of the HSM Part C
● Policy Review Module (PRM) ⇒ Faithful review of the AASHTO Green Book
● Design Consistency Module (DCM)
● Intersection Review Module (IRM)
● Traffic Analysis Module (TAM)
● Driver/Vehicle Module (DVM)
● Economic Analysis Tool
● Administration Tool (including Calibration utility)
(Cont.)
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IHS
DM
Mo
du
les
Substantive Safety
Nominal Safety
(Cont.)
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(Cont.)
Pennsylvania: PA I-70 Yukon/Madison Interchanges
18Source: Michael Dimaiuta, Mohamad Banihashemi, Pennsylvania’s Use of IHSDM for a Safety Analysis of Freeway
Interchange Design Alternatives on I-70, TRB 2016
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(Cont.)
Maryland: Finding hot-spots on MD-100 using IHSDM
20Source: Seyedehsan Dadvar et al., Complexity vs. Predictability: Evaluation of Different Levels of HSM Predictive
Methods on Maryland Route 100, TRB 2017
(Cont.)
Colorado: Ramp reconfiguration & restriping alternatives safety analysis using IHSDM
21Source: Michael Dimaiuta, Mohamad Banihashemi, Jacob Southard, Colorado I-225/I-25 Ramp Reconfiguration and
Restriping Alternatives: Safety Analysis Using IHSDM, TRB 2018
Existing
Note: Due to using uncalibrated models, numbers are valid
for alternative comparison only.
(Cont.)
Minnesota: Connection safety analysis using IHSDM
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Source: Ellen Nightingale, Brandon Yarbrough, US-31 at I-94 Connection Alternative Analysis, TRB 2020
(Cont.)
Wisconsin DOT Safety Certification Process Development
● Incorporating HSM & IHSDM in the process
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Source: Lee Gibbs, Identify Cost-Effective Safety-Driven Improvements for Roadways, TRB 2020
(Cont.)
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Example of Economic Analysis on a freeway segment:
● 3.8 mile section
Base Case:
● Shoulders vary from 4 ft to 10 ft
● Lane widths vary from 10.6 ft to 13 ft
Alternative 1 ⇒ Widening all shoulders to 10 ft
Alternative 2 ⇒ Changing lane widths to 12 ft
(Cont.)
Example of Economic Analysis on
a freeway segment (Cont.)
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Crash Modification Factor (CMF) Clearinghouse
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Source: FHWA Safety Data and Analysis: Application of CMFs
(Cont.)
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Source: FHWA Safety Data and Analysis: Application of CMFs
(Cont.)
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Source: FHWA Safety Data and Analysis: Application of CMFs
(Cont.)
● The CMFs quantify the expected
changes in crashes compared to base
conditions due to given countermeasures
or existing conditions at applicable sites.
● The CMF Clearinghouse is a web-based,
comprehensive, and searchable
database of published CMFs:○ Illuminating an unlighted road segment
○ Paving gravel shoulders
○ Signalizing a stop-controlled intersection
○ Choosing a signal cycle time of 70 seconds
instead of 80 seconds
○ etc.29www.cmfclearinghouse.org
(Cont.)
As of Feb. 10th, 2020:
● 1,203 countermeasures
● 8,310 CMFs○ 7,288 CMFs (star-rated)
○ 1,022 CMFs (non-star-rated)
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(Cont.)
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(Cont.)
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(Cont.)
Comparison table of
selected CMFs:
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(Cont.)
Top 20 countermeasures on CMF Clearinghouse by number of CMFs:
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(Cont.)
State Selected CMF Lists
● Help practitioners to
find appropriate CMFs
● Consistency in CMF
use across the state
35As of July 2019
&
New feature in IHSDM (Ver. 15.0.0):
● The capability for users to define and apply “User-defined CMFs”
● The CMFs can be from CMF Clearinghouse and other sources
● The locally-developed CMFs can be used as well.
● Currently, “User-defined CMFs” can be entered by crash severity (FI, PDO, & Total)
36Example application: Curve radius CMF for multilane arterials
Conclusions
The HSM / IHSDM / CMF Clearinghouse have broad applications:
● Identify sites with the most potential for crash reduction
● Recognize factors contributing to crashes
● Find associated countermeasures to address the issues
○ CMF Clearinghouse (more than 8,000 CMFs)
● Conduct economic appraisals of improvements and prioritize projects
● Assist practitioners in their RSAs
○ IHSDM can be a handy tool to compare alternatives and make informed decisions.
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FHWA Training
● National Highway Institute (NHI) Training
○ HSM Practitioner's Guide Courses (NHI 380070), (NHI 380070A), and (NHI 380070B)
○ Interactive Highway Safety Design Model (NHI 380071) & more
● Safety Data and Analysis Training videos
○ Predictive method, Observed, Expected Predicted Crashes
○ Application of CMFs, Selecting / Applying a Method to Analyze Multiple CMFs & more
● Resource Center Training
○ FHWA Practitioner’s Workshop for the Highway Safety Manual
○ FHWA HSM Roadway Safety Management Process & more
38https://safety.fhwa.dot.gov/rsdp/training.aspx
Seyedehsan (Ehsan) Dadvar, Ph.D., RSP1
National Research Council (NRC) Research Associate
Geometric Design Laboratory (GDL)
Turner-Fairbank Highway Research Center (TFHRC)
Federal Highway Administration (FHWA)
(202) 493-3134
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