Slide 1
Dr. Mohamadreza Banihashemi
Senior Transportation Research Engineer II
GENEX Systems
University of Maryland Seminar
November 2014

Slide 2
ENCE688F: Highway Safety Fundamentals
• History and Trends
• Definitions and Concepts
• Crash Studies and Crash Data
• Crash Prediction Models
• Major National Highway Safety Programs, HSM and SHRP2
• Software Packages, Databases (i.e., SHRP2 RID)
• IHSDM, a Course Project
Implementation of the HSM in the IHSDM Software
• Highway Safety Manual (HSM) Overview
• IHSDM Overview
• Relationship between HSM and IHSDM
• Use of IHSDM / HSM in Developing a Sustainable Highway
System
• Questions / Discussion .

Slide 3
ENCE 688F:
Highway Safety Fundamentals
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A Graduate Course Focusing on
Highway Safety History and Trends
Definitions and Concepts
Crash Studies and Crash Data
Highway Safety Quantitative Evaluation
Crash Prediction Models
Major National Highway Safety Programs
Software Packages, Databases (i.e.,
SHRP2 RID)
Course Project (IHSDM Software) .

Slide 4
A Highways Safety Manual Course, or
An IHSDM Software Course, or
A SHRP2 Safety Program Training.
This is a Course in Highway Safety
Fundamentals including many components of the above !!

Slide 5
Organizations:
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Federal Highway Administration (FHWA)
● Federal-Aid Program
● MUTCD
● Software/Website Development
● Actively Supporting HSM
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Transportation Research Board (TRB)
● Highway Safety Manual (HSM) 1 st Edition
● SHRP2
● Toward HSM 2 nd Edition
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American Association of State Highway and
Transportation Officials (AASHTO)
● Highway Safety Manual (HSM)
● Some Other Programs
● HSM Publication and Support .

Slide 6
-Continue
● Highway Crash Fatality Trend
● The First Period of Rising Automobile Use in the US
● First National Conferences on Street and Highway
Safety
● Balanced Design for Safety, Design Speed Concept
● Early Studies on the Effect of Highway Geometry on Safety
● An Erroneous Study Result: “The Accident Prone
Driver”
● National Programs of Research and Development .

Slide 7
Definitions and Concepts
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Introducing main highway safety concepts and measures:
Design Speed Concept and its Deficiencies
Nominal Safety Measures
Substantive Safety Measures
Surrogate Safety Measures (Diagnostic
Safety)
• Operating Speed
• Near Crash .

Slide 8
Definitions and Concepts
-Continue
Major Factors Known as Causes of
Crashes
• Human
• Vehicle
• Highway
• Environment
Cause and Effect vs. Correlation
• Older drivers and crash severity
• Speed and crash severity .

Slide 9
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Highway Purpose and Functional
Classification
• Mobility vs. Access
Functional Classification Effects on
Highway Design
Design Factors Affecting Safety the
Most
Some National Crash Characteristics and Trends .

Slide 10
Highway Characteristics and Safety
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Major Highway Characteristics by
Functional Class
Traffic Volume
Traffic Control
Highway Geometry
Auxiliary Lanes
Roadside
Lighting
Speed Enforcement .

Slide 11
Intersection/interchange Characteristics and Safety
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Major Intersection Characteristics by
Functional Class
Volume
Traffic Control
Intersection Layout/Skew Angle
Interchange Configuration
Turn Lanes/Islands
Lighting .

Slide 12
Roundabout, A New Type of Intersection
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Traffic Circles (Rotaries)
Neighborhood Traffic Circles
Modern Roundabouts
• Yield control
• Channelization
• Geometric curvature to limit the speed
Safety Effect of Replacing
Intersections with Roundabouts
New Researches on Roundabouts .

Slide 13
Types of Crash Data and Crash Studies
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Observational vs. Experimental Data
Longitudinal vs. Cross Sectional Data
Panel Data
Before-and-After Data
Some Sources for Inconsistencies and
Biases
Basic Types of Highway Safety Studies
• Naïve and Improved Before-After Studies
• Cross Sectional Studies
• Empirical Bayes Studies .

Slide 14
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National highway Traffic Safety
Administration (NHTSA)
• National Automotive Sampling System (NASS)
• Fatality Analysis Reporting System (FARS)
• Crashworthiness Data System (CDS)
• General Estimates System (GES)
Highway Safety Information System
(HSIS)
Other State Data
GIS Data
NDS Data Collected in SHRP2 Project .

Slide 15
Common Types of Crash Prediction Models
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Main Assumptions
• Crash count obeys Poisson probability law
• Estimates of crashes follow Gamma distribution
Most Common Models
• Negative Binomial
• Linear and Non-Linear Regression
Models with Crash Modification Factors
• Safety Performance Functions
• Crash Modification Factors
Empirical Bayes Process .

Slide 16
Highway Safety Manual (HSM)
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Part A – Introduction & Fundamentals
• Chapter 1 Introduction and Overview
• Chapter 2 Human Factors in Road Safety
• Chapter 3 Fundamentals
Part B – Safety Process
• Chapter 4 Network Screening
• Chapter 5 Diagnosis
• Chapter 6 Selection of Countermeasures
• Chapter 7 Economic Appraisal
• Chapter 8 Prioritization of Improvement Projects
• Chapter 9 Safety Effectiveness Evaluation .

Slide 17
More on Highway Safety Manual (HSM)
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Part C – Predictive Methods
• Chapter 10 Rural, Two-Lane Roads
• Chapter 11 Rural, Multilane Highways
• Chapter 12 Urban/Suburban Arterial Highways
Part D – Accident Modification Factors
• Chapter 13 Roadway Segments
• Chapter 14 Intersections
• Chapter 15 Interchanges
• Chapter 16 Special Facilities & Geometric Situations
• Chapter 17 Road Networks
Part C – HSM Supplement
• Chapter 18 Freeways
• Chapter 19 Ramps.

Slide 18
SHRP2 Safety Program
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A Quick History
What Is Naturalistic Driving Study
(NDS)?
Collecting NDS Data
SHRP2 Roadway Information Data (RID)
Collecting and Assembling RID
Using NDS in Conjunction with RID
Brain Storming .

Slide 19
Course Project, IHSDM Software
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Highway Safety Concepts Used in Each
Module
Setting Attributes
Mechanics of the Software
A Quick Review of Administrative Tool
Running the IHSDM Software
Reporting and Customizing Report
Templates
Interpretation of Results .

Slide 20

Slide 21

Slide 22
HSM, Background, History, and Future
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Joint Task Force sponsored by several TRB committees
Partnership Among AASHTO, TRB and FHWA
$7 Million/10 year research program
Thousands of hours of volunteer effort of reviewing
AASHTO Joint Task Force with members from Safety,
Design and Traffic Engineering
Publication of the HSM by AASHTO (2010), Supplement
(2014)
A new TRB Committee (Highway Safety Performance)
Works to complete HSM 1 st Edition and moving toward 2 nd
Edition .

Slide 23
Part A
Introduction,
Human
Factors, and
Fundamentals
Part B
Roadway
Safety
Management
Process
Part C
Predictive
Method
Part D
Crash
Modification
Factors

Slide 24
Nominal
Safety
Substantive
Safety
The expected or actual crash frequency and severity for a highway or roadway
Examined in reference to compliance with standards, warrants, guidelines and sanctioned design procedures

Slide 25
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A product of FHWA’s Safety Research and
Development Program
A suite of software tools that support project-level geometric design decisions by providing quantitative information on the expected safety and operational performance
Free Distribution and Support, First
Release 2003, Latest Release 2014 .

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Crash Prediction
Policy Review
Design Consistency
Intersection Review
Traffic Analysis
Driver/Vehicle

Slide 27
Faithful implementation of the HSM Part C
Estimates expected crash frequency (i.e.,
Substantive Safety ) as well as crash severity based upon roadway geometry and traffic volumes .

Slide 28
Relationship between IHSDM and the HSM
A.
Introduction and Fundamentals
B.
Roadway Safety Management Process
C.
Predictive Method (IHSDM CPM)
Chapter 10: Rural, Two-Lane Roads
Chapter 11: Rural, Multilane Highways
Chapter 12: Urban & Suburban Arterials
Chapters 18 and 19: Freeways and Ramps. Recently published as supplements to the 1 st edition of the HSM.
D.
Crash Modification Factors .

CPM / HSM Part C Scope
Slide 29
From AASHTO Website: An Introduction to Highway Safety Manual

Slide 30
CPM / HSM Part C Scope -
Continue
HSM Chapter
18 Freeway Segments
18 Speed-change Lanes
19 Ramps and C-D
Roads
19 Ramp Terminals
Urban
10 Lanes
10 Lanes
2 Lanes
7 Types
Rural
8 Lanes
8 Lanes
1 Lanes
7 Types

Slide 31
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Safety Performance Functions (SPFs)
Crash Modification Factors (CMFs)
Empirical Bayes (using crash history data)
Calibration Factors
• Enter via IHSDM Administration Tool .

Slide 32
Maximizing Safety Improvement Benefits in A
Sustainable Highway System
• Construction Cost
• Operational Costs, Users Cost
• Environmental Costs
• Crash Cost.

Maximizing Safety Improvement Benefits in A
Sustainable Highway System
Continue
Network-level Maximization, Part B of the HSM
Slide 33
From AASHTO Website: An Introduction to Highway Safety Manual

Slide 34
Maximizing Safety Improvement Benefits in A
Sustainable Highway System
Continue
Project-level Maximization, Part C of the HSM
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Predicting Crashes for Different Alternatives
Estimating Construction, Operational,
Environmental, and Crash Costs for Different
Alternatives
Search for the Alternative with the Minimum
Total Cost .

Slide 35
Other IHSDM Modules, Policy Review
Checks roadway segment geometry against relevant design policy and “flags” variations .

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Other IHSDM Modules, Design Consistency
Estimates 85th percentile speed profile along alignment to evaluate operating speed consistency .

Slide 37
Other IHSDM Modules, Traffic Analysis
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Traffic simulation model
(TWOPAS)
Estimates traffic quality of service measures .

Slide 38
Other IHSDM Modules, Driver / Vehicle
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Simulates driving behavior and vehicle dynamics on a two-lane highway
Provides profiles of predicted speed and other response variables, via a simulation of a single driver/vehicle combination .

Slide 39
Other IHSDM Modules, Intersection Review
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Expert system that applies rules of good practice in a comprehensive diagnostic review of a single intersection
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Identifies possible safety concerns and typical treatments .

Slide 40
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May be downloaded free-of-charge at: http://www.ihsdm.org
Technical support:
• E-mail: IHSDM.Support@fhwa.dot.gov
• Phone: (202)-493-3407
IHSDM Training (Offered by NHI):
• FHWA-NHI-380071 On-site Course
• FHWA-NHI-380100 Web-based Course
( http://nhi.fhwa.dot.gov
)