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HIGHWAY SAFETY MANUAL Copyright © 2016 STC, UK HIGHWAY SAFETY MANUAL Copyright © 2016 STC, UK

HIGHWAY SAFETY MANUAL Copyright © 2016 STC, UK - PowerPoint Presentation

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HIGHWAY SAFETY MANUAL Copyright © 2016 STC, UK - PPT Presentation

Learning Outcomes Introduce the Highway Safety Manual Define procedures and techniques Demonstrate use of Safety Performance Functions Crash Modification Factors Safety always comes first in everything we do ID: 757775

hsm safety crash spf safety hsm spf crash crashes part aadt factors lane cmf design roadway modification predictive performance

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Slide1

HIGHWAY SAFETY MANUAL

Copyright © 2016 STC, UKSlide2

Learning Outcomes

Introduce the Highway Safety ManualDefine procedures and techniquesDemonstrate use of

Safety Performance Functions

Crash Modification FactorsSlide3

Safety always comes first

in everything we do!Slide4

Safety & Roadway Design

Each design assumes a safety levelSection 109, Title 23, USC

Need for balancing of safety, mobility, economic considerations, protection and enhancement of natural environment, and preservation of community values

Tradeoffs among design, cost, and safetySlide5

Decision Making Process

Environment

Costs

Society

Safety

Capacity

Right of WaySlide6

Basic Safety Questions?

How can I predict safety performance of geometric design features?How can I quantitatively calculate safety effects?

How can I justify decisions based on safety implications? Slide7

Highway Safety Manual Purpose

Resource for professionalsSafety knowledgeDecision making toolsSlide8

The HSM is…

Analysis toolEstimations of safety performance

Prediction of crashesSlide9

The HSM is NOT…

Best Practice guideWarrantsStandardsSlide10

HSM 2010Slide11

A Safe Roadway?

List what are the top three items that make a roadway safe

1

.

2.

3. Slide12

Safe Roadway?Slide13

Safety Levels

Nominal safetyMeasured as compliance to standards, warrants and guidelines

Yes/No

Substantive safety

Measured by crash frequency and severity

Continuous scaleSlide14

Nominal vs. Substantive Safety

Design Value

Crash RiskSlide15

HSM ToolsSlide16

Crash Prediction Uses

Program levelSegment prioritizationProject level

Project needs assessment

Communication with the public

Documentation

Tort DefenseSlide17

HSM Contents

Introduction, Human Factors, Fundamentals

Safety Management Process

Predictive Methods

Crash Modification FactorsSlide18

HSM Companion Software

HSM Part

Supporting Tool

Part B:

Roadway Safety Management Process

SafetyAnalyst

www.safetyanalyst.org

Part C: Predictive MethodsIHSDMwww.ihsdm.orgPart D: Crash Modification Factors

FHWA CRF/CMF Clearinghousewww.cmfclearinghouse.orgSlide19

Some More Questions

What is the number of crashes for a given scenario?2-lane rural road with 5,000 AADT

4-lane rural arterial divided arterial with 20,000 AADT

What will be the safety effect if we

Widen shoulder

Add a median

Add a left-turn laneSlide20

How HSM Works

Safety Performance Function(SPF): regression equationCrash Modification Factor (CMF): adjustment factors

Calibration Factor (C): local adjustment

SPF

CMF

C

Predicted

CrashesSlide21

Part C: Predictive Methods

(1/3)

Safety Performance Functions (SPFs)

Regression models

Predict expected crash frequency

Developed from data for a number of similar sites

Developed for specific site types and “base conditions”

SPFSlide22

SPF Development

Average Daily Traffic (ADT)

Crashes/Year

SPF Slide23

SPF Example: 2-Lane Rural Roads

N

spf rs

= AADT x L x 365 X 10

-6

x e

(-0.312)

(Eq. 10-6)Note: assumed crash type and severity distribution Slide24

Part C: Predictive Methods

(2/3)

Crash Modification Factors (CMFs)

Adjusts SPF predicted value

Accounts for differences between base and site specific conditions

CMFSlide25

Part C: Predictive Methods (3/3)

Local calibration factor (Cr)

Adjusts SPF from HSM to local conditions

Addresses local variations

CSlide26

HSM Prediction Models

Prediction models forHomogeneous highway segments Intersections

Segments based on homogeneous

Geometry

AADT rangesSlide27

Segments and IntersectionsSlide28

HSM Process

Segment Facility

Geometry, AADT

Define Data

Limits, Type, Time, Geometry, AADT

Predict Crashes

SPF

Adjust Crashes

CMF, CSlide29

Cross Sectional ElementsSlide30

Safety and Operational Effects

Lane Width

Shoulder Width

Sideslope

Clear Zone

Crashes Operations

Head-on Capacity

Wider is “better” Wider means “faster” Run-off-Road Capacity Wider is “better” Functionality Run-off-road (severity) Maintenance Flatter is better Flatter is better Run-off-road Horizontal sight (frequency and severity) distance