making the most of the highway safety...

Making the most of the Highway Safety Manual

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APWA Monterey Bay Training Conference June 28, 2016 Watsonville, CA Matt Braughton Kittelson & Associates, Inc.

Agenda

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Highway Safety Manual (HSM) 1st Edition HSM Principles

HSM Applications HSM Part A – Introduction and Safety Fundamentals HSM Part B – Roadway Safety Management Process HSM Part C – Predictive Method HSM Part D – Crash Modification Factor

Corridor Example US 12 in Washington State

HSM Tools The Future HSM 2nd Edition Fixing America's Surface Transportation (FAST) Act Caltrans Transportation Analysis Guide (TAG)

HSM Principles

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The Highway Safety Manual…. Helps professionals support design decisions

Are 11 foot lanes different than 12 foot lanes?

Helps agency staff communicate with upper management, elected officials and the public. Why didn’t you put a signal there?

Saves money and helps better manage limited budgets.

Do we really need to buy that property to close that driveway?

Safety can be the differentiator between alternative solutions.

Safety as a priority is a federal initiative with increasing attention and increasing amounts of funding associated with it.

Why do something different?

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Able to measure safety objectively (i.e., quantitatively) New tools build on and enhance current practice Improve reliability Provide new capabilities (e.g., predicting crashes) Able to quantify safety and compare with other project advantages and

disadvantages

Opportunities to incorporate new tools and methods in the near-term and plan for further integrating them in the long-term No need to do everything at once New tools/methods can provide value to decision making now

Integrating Safety

Safety integration throughout project development process Quantify safety performance Comprehensively address safety issues Cost-effectively reduce crashes

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What is the HSM and how can it be used?

Quantifying Safety in Project Decisions Spending Limited Resources Wisely Guiding Improvements for...

– Networks – Corridors – Intersections

Managing Risk to Reduce Tort Liability

Agenda

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HSM Content

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Part A – Introduction and Fundamentals 1: Introduction 2: Human Factors 3: Fundamentals

Part B – Roadway Safety Management Process 4: Network Screening 5: Diagnosis 6: Select Countermeasures 7: Economic Evaluation 8: Prioritization 9: Safety Effectiveness

Evaluation

Part D – Crash Modification Factors 13: Roadway Segments 14: Intersections 15: Interchanges 16: Special Facilities 17: Networks

Glossary

Part C – Predictive Method 10: Two-Lane Rural Highways 11: Multilane Rural Highways 12: Urban and Suburban Arterials

Plus… subsequently published “chapters” on various topics (i.e., Freeways and Interchanges)

Part A – Introduction and Safety Fundamentals

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Factors Influencing Crashes

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Nominal Safety vs. Substantive Safety

Source: NCHRP 480

Objective and Subjective Safety

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“Downtown is difficult as it is without having a roundabout death trap in it.” - Chico Enterprise - Record Posted: 03/08/2011

Objective – Measured

Subjective - Perceived SUBJECTIVE

Converting a traffic signal in an urban area to a roundabout reduces injury/fatal crashes by about 60%. – HSM 2010

OBJECTIVE

Preferred Measure of Safety: Long Term Expected Average Crashes

Considered more reliable measure – minimizing influence of the randomness of crashes

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0 5 10 15

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Years

Crashes Average

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Regression to the Mean

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Presenter

Presentation Notes

It is an important phenomenon to take note of in conducting experiments because it affects the internal validity of the experimental design. What happens here is that one can end up concluding that the significant difference or effect is due to the treatment when in fact it is due to chance and by this phenomenon known as regression toward the mean. It occurs whenever the sample or subjects are chosen on the basis of extreme pretest scores. Examples of this are students with the worst math ability, workers with the lowest morale or patients with the most severe symptoms. Regression toward the mean is expected in these cases where there is non-random sampling or assignment in experiments. There are cases of experimental designs where the researcher tries to improve on the random group designs by conducting more stringent tests of their hypotheses. This is usually done by comparing groups in the extremes of the distribution of the sample. Through this, they hope to show that groups who start out very different (i.e. from opposite ends of the spectrum), can be made to become more alike when one of the experimental groups is given the treatment. An example of such an experiment is the testing of a math program that is postulated to help students who are poor in their math ability. Researchers who want to make their tests more stringent would treat the group of students who is the poorest in their math ability and compare them to the group who is good in their math ability. Shaughnessy and Zechmeister (1990) explains that when one takes a measurement in an experiment, the measurement is made up of two components; the true score/measure and the error. The true score reflects what the test is validly measuring and tends to be stable from one measurement to another. The error component includes extraneous factors which are nonsystematic. These can include lack of concentration, inappropriate testing conditions or improper question wording. This component is the part that averages out from one measurement to another. According to Shaughnessy and Zechmeister (1990) , what this means is that an individual who scored extremely high on the first test is "likely to score lower on a second test simply because the error component is like to be less extreme and closer to the average." They mentioned that the less reliable the test, the more likely regression toward the mean will occur.

Part B - Roadway Safety Management Process

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Roadway Safety Management Process

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Why invest resources in a safety management program? Key for cost effectively reducing crashes on roadways

TRB Special Report 300: Achieving Traffic Safety Goals in the United States U.S. lags behind other developed countries

Enables you to know where opportunities to improve exist Better positioned for funding Better equipped to reduce crashes with each dollar invested

What is a Roadway Safety Management Program? Multidisciplinary in scope – engineering, enforcement, education,

evaluation Includes meaningful goals, milestones, focus locations, treatments and

evaluating effectiveness

Roadway Safety Management Process Chapters in Part B

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Network Screening

What sites have potential

for improvement?

Diagnosis

What pattern do crashes follow?

Select Countermeasures

What factors contribute to

crashes?

Economic Appraisal

What countermeasures

are cost-effective?

Prioritize Projects

What projects meet program objectives?

Safety Effectiveness

Evaluation

How effective were countermeasures?

Example: City of Pasadena Safer Streets Program

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Purpose: Establish a process for identifying, prioritizing, and intervening at specific locations to reduce crashes

City of Pasadena Safer Streets Program

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Context Motivated by desire to have a repeatable, technically sound process for

identifying and prioritizing safety investments Funded through Caltrans Office of Traffic Safety Grant Completed in September 2015

Scope of Activities Conducted city-wide crash analysis Integrated methods from Part B into existing City tools and practices Identified initial set of locations for field reviews Conducted field reviews and documented range of potential treatments

to reduce crashes


Integrated methods from Part B… Reviewed and evaluated potential

network screening performance measures from the HSM

Identified performance measures for

near-term implementation Identified performance measures for

longer-term implementation Differentiation between near- and long-

term implementation based primarily on data needs and availability


Incorporated three network screening performance measures from the HSM Critical Crash Rate Excess Proportion of a Specific Crash Type Probability of Specific Crash Types Exceeding a Threshold Proportion

Presenter

Presentation Notes

Critical Crash Rate Identities locations performing worse than their peers Considers traffic volume and historic crash data Reduces exaggerated effect of sites with low traffic volumes Excess Proportion of a Specific Crash Type Identifies locations with a larger proportion of a certain crash type compared to its peers e.g., Could identify signalized intersections with a greater proportion of left-turn crashes Probability of Specific Crash Types Exceeding a Threshold Proportion Identifies locations where it is likely a specific crash type exceeds and is likely to continue to exceed a threshold e.g., Could identify signalized intersections where left-turn crashes are mostly likely to be a long-term issue unless a treatment or change is implemented


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Conducted Field Reviews and Identified Potential Changes Focus Intersection #1 Traffic Signal Control Observations

Intersection slightly skewed EB and WB left-turn movements

offset Signal phasing protected-permitted 33% of crashes occurred at night Bus stops and driveways adjacent to

intersection


Focus Intersection #1 – Example Concept


Conducted Field Reviews and Identified Potential Changes Focus Intersection #2 Two-way Stop Control

Intersection Observations

Minor street approaches offset Adjacent to school Uncontrolled crosswalk with in-

pavement flashing lights Bus stops adjacent to

intersection Flashing beacons for school

zone close to crosswalk treatments

City of Pasadena Safer Streets Program Focus Intersection #1 – Example Concept


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Example Summary of Potential Treatment Effectiveness

Treatment CMF Treatment

Name CMF Standard

Error

Potential Crash

Reduction Crash Type

and Severity

Road Diet Four to Three Lane Conversion

0.71 0.02 25% to 33% All Types, All Severities

Extend Red Curb Markings

Improve Triangle Sight Distance

0.63 -- 37%

All Types Series and Minor Injury Severities


0.89 0.15 8% to 14%

All Types, Property Damage Only Severity


0.44 -- 56% All Types, Fatal Severity


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Outcomes Enables City to prioritize locations and investments on regular basis Improves responsiveness to local decision-makers Facilitates incorporating safety improvements into a range of different

activities Enables City to proactively apply for grants and other funding

Part C – Predictive Method

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Overview of Methods for Estimating and Predicting Crashes

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Why estimate or predict crashes? Identifying potential countermeasures Designing new roadway and want to consider safety quantitatively Modifying existing roadway and want to consider safety quantitatively

What types of projects could this apply to? Corridor studies Intersection studies Access Management activities Capacity enhancements Development review process “Upgrades to an urban cross-section”

Overview of Methods for Estimating and Predicting Crashes

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Traditional Approach Surrogates for Safety (e.g., standards, speed, number of conflict points)

Advantage – Simple and familiar Disadvantage – Indirect measures, need an existing condition

Crash Reduction Factors Advantages – Simple and limited data Disadvantages – Unreliable results (does not account for RTM), not always

able to account for variability in results

New Approaches HSM Predictive Method

Advantages – More reliable results (accounts for RTM), do not need an existing condition

Disadvantages – Slightly more expertise and data needed Crash Modification Factors (Discussed this afternoon)

Advantages – More reliable, able to account for variability in results Disadvantages – Slightly more expertise and data needed

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What is the Predictive Method?

Estimate Crashes per Year

Condition 1

Condition 2 P

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rtesy

of Y

olan

da T

akes

ian

When can you use the Predictive Method?

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Any time comparing changes crash frequency due to changes in cross-section or changes in traffic volume

Example Application

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Powell Boulevard – Arterial Corridor Evaluation The Scenario:

A heavily used urban arterial in need of improvements Traditional traffic operations analysis did not find any clear “winners” among

the alternatives

The Question: Which alternative will best serve future needs of the corridor?

The Project Activities:

Conducted Safety and MMLOS evaluations Quantified Predicted Safety trade-offs between concepts

The Result:

Allowed ODOT to consider quantified safety information in their selection process

Arterial Corridor Context

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Group Description 1 Access Management and Intersection Modifications at 122nd 2 Different locations of left-turn lanes along SE Powell

Boulevard 3 Three-lane (TWLTL) roadway with different roadway element

widths 4 Three-lane (raised median) roadway with different roadway

elements 5 Existing conditions with different pedestrian features

Test these alternatives using HSM Predictive Method

Year 2020 Analysis Results

Alt Group

Description % Crash Reduction

1 Access Management and Intersection Modifications near 122nd 0%1

2 Different locations of left-turn lanes along SE Powell Boulevard 1-3%2

3 Three-lane (TWLTL) roadway with different roadway element widths

21%

4 Three-lane (raised median) roadway with different roadway elements

19-27%3

5 Existing conditions with different pedestrian features 0%1

The Result: – Allowed ODOT to consider quantified safety information in their

selection process – Comprehensive assessment of alternatives created a better

understanding of tradeoffs

Presenter

Presentation Notes

Sidewalks provided MMLOS benefits Documented Auto/Ped crashes require crossing treatments Potential crash reduction from median (vs TWLT) did not offset widening that would be required at intersections

Part D – Crash Modification Factors

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HSM Part D CMFs

Part D CMFs were included in HSM through a filtering process A Part D CMF will not adequately adjust an SPF to site-specific conditions Part D CMFs are standalone and may be applied more broadly. General application guidance is provided in the HSM. No more than THREE Part D CMFs should be multiplied with each other**

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CMF Standard Error in HSM Part D Chapters

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CMF Standard Error

CI = confidence interval

CMFx = CMF for condition x

SEx = Standard error for condition x

Analysis result will yield a range with 95% Confidence

xx SE2CMF(95%) IC ×±=

Additional CMF Resource

FHWA CMF Clearinghouse Over 2500 CMFs

Over 700

countermeasures

Star Rating

http://www.cmfclearinghouse.org/

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http://www.cmfclearinghouse.org/

Example Application

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US 26 at Dover Lane Road Safety Audit Project

US Highway intersection road safety audit Basic Project Question

What safety issues are present and how can they best be mitigated?

Project Activities

Crash history review Road safety audit Mitigation benefit/cost analysis for

high risk features Scoping letter to ODOT for safety

mitigations

US 26 at Dover Lane RSA

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Intersection skew Obscured line of sight Deficient signing and striping

US 26 at Dover Lane RSA – Benefit/Cost

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Mitigation benefit/cost analysis (a 3-page memo) Assembled crash reduction factors (CRF)

Estimated mitigation benefits: $241,000/year Estimated mitigation costs: $731,000 Benefit/cost ratio: 4.1

US 26 at Dover Lane RSA

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Value to ODOT Expanded RSA effort to identify and

evaluate mitigations

Quantifiable safety benefits allow for benefit/cost and other project evaluation methods

Agenda

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US 12 Corridor Study: Integrating the HSM and Performance-Based Design Decisions

July 30, 2013 Erin M. Ferguson, P.E. Brian L. Ray, P.E.

Context – Study Scope

Building off of a previous WSDOT Study A set of initial improvements

identified from WSDOT Those improvements were also

evaluated within project

Overarching Activities of the Project Review and Assess Crash Data

from MP 36 to 41 Identify Potential Improvements (in

addition to WSDOT Improvements) Evaluate Potential Safety Benefits

using Highway Safety Manual Compare Estimated Safety

Benefits and Costs

US 12 Study Corridor in Washington State

Context - Corridor-Wide Observations

Centerline Rumble Strips Present Paved Shoulders 2 to 4 feet in Width Western Portion of Corridor Relatively Steep Roadside Slopes Standing Water in Roadside Ditches

Westbound on US 12 from Sickman-Ford Rd

Eastbound along US 12 east of Blockhouse Road

Context - Corridor-Wide Observations

Limited Visibility of Minor Road Intersections Observed Logging and Aggregate Trucks

SR 12 at Blockhouse Road

Eastbound Approach to SR 12/Blockhouse Road Intersection

Context – Corridor Wide Observations

Speeds along the corridor generally exceed 55 mph

Posted Speed is 55 MPH

Approach

Identify historic crash trends and patterns Define an improvement tool box Identify and evaluate potential solutions from the tool box Develop an interim and long-term safety improvements plans

Findings – Historic Crash Patterns and Trends

Crash Types at Intersections Angle and Turning Crashes - 55% of total crashes Rear End Crashes – 26 % of total crashes

Crash Types on Roadway Segments Roadway or Lane Departure – 53 % of total crashes

Fixed Object (Left the roadway and struck a fixed object) Vehicle Overturned (Generally, left the roadway and overturned)

Contributing Factors at Intersections Failure to Yield Right-of-Way – 29% Excessive Speed -16%

Contributing Factors on Roadway Segments Excessive Speed – 26% Fatigue or Inattention – 23% Under the Influence – 9% Improper Passing – 4%

Findings – Sample of Improvement Toolbox

Increase intersection and driver awareness

Based on NCHRP Report 613, Exhibit 3-1


Increase intersection and driveway awareness

Pennsylvania – FHWA-HRT-08-063, Figure 9

NCHRP 613, Exhibit 4-2 (TXDOT)

Pennsylvania – FHWA-HRT-08-063, Figure 3


Consider range of intersection traffic control

Findings – Identify and Evaluate Potential Solutions


Estimated Cost-Effectiveness of Potential Improvements Calculated the cost per crash reduced over the design life of the improvement Used planning level cost-estimates Estimated change in crashes per improvement Incorporated 5-year design life for near-term improvements and 20-year

design life for long-term improvements


Draft Priority

Time Frame Location - Improvement

Expected Crashes/Yr

A

Estimated Percent

ReductionB

Planning Level Cost EstimateB

$/Crash Mitigated

Over Design Life

1N Near-Term Anderson Road Intersection- FHWA Lane Narrowing 2.2 31% $45,000 $13,196

2N Near-Term Anderson Road Intersection- FHWA Splitter Island 2.2 68% $112,500 $15,040

3N Near-Term Moon Road- FHWA Lane Narrowing 1.9 31% $45,000 $15,280

4N Near-Term Moon Road- FHWA Splitter Island 1.9 68% $112,500 $17,415

5N Near-Term Forstrom Road- FHWA Lane Narrowing 1.1 31% $45,000 $26,393

6N Near-Term Forstrom Road- FHWA Splitter Island 1.1 68% $112,500 $30,080

1L Long-Term Forstrom Road- Left Turn Lanes 1.1 48% $330,000 $31,250

- Near-Term Blockhouse Road - FHWA Lane Narrowing 0.9 31% $45,000 $32,258

- Near-Term Blockhouse Road- FHWA Splitter Island 0.9 68% $112,500 $36,765

2L Long-Term Blockhouse Road - Left Turn Lanes 0.9 48% $330,000 $38,194

3L Long-Term Moon Road- Access Restriction / Right Turn Lane 1.9 26% $610,000 $61,741

4L Long-Term Anderson Road- Single Lane Roundabout 2.2 71% $3.15

million $100,832

- Near-Term Sickman- Ford Road- FHWA Lane Narrowing 0.2 31% $45,000 $145,161

- Near-Term Sickman- Ford Road - FHWA Splitter Island 0.2 68% $112,500 $165,441

- Long-Term Sickman- Ford Road - Left Turn Lane 0.2 43% $330,000 $191,860

- Long-Term Anderson Road - Traffic Signal 2.2 36% $5.61 million $354,167

- Long-Term Blockhouse Road- Realign 0.9 19% $1.5 million $438,596

Findings – Interim Safety Improvement Plan

Findings – Long-Term Safety Improvement Plan

Agenda

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HSM Tools

SafetyAnalyst by AASHTOWare Roadway Safety Management Tool

Implements Part B methods from HSM – Network-level review – Site-level treatments – Network-level prioritization

Incorporates benefit/cost prioritization methodology Performs effectiveness evaluation to determine safety benefits of treatments More information at http://www.safetyanalyst.org/

Software cost Single Work Station: $15,000/year Site License: $25,000/year

http://www.safetyanalyst.org/

HSM Tools

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PlanSafe Planning-level safety performance analysis tool

Uses travel demand model output and crash data Provides ability to incorporate safety at planning level

Can be used to define safety performance measures Compare growth scenarios and large-scale projects

Limited to planning analyses Cannot evaluate site-specific safety treatments Should not be used to select land use or transportation investments

Data Needs Census and Zonal Data GIS Shapefiles Crash Data

Software cost Free More information here: http://www.trb.org/Main/Blurbs/163790.aspx

http://www.trb.org/Main/Blurbs/163790.aspx

HSM Tools

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HiSafe Calculate most stable performance measure, expected average crash

frequency Cost: $500 per license, no annual fee; sliding scale for multiple licenses More information available at: www.hisafe.org

NCHRP Spreadsheets Calculate most stable performance measure, expected average crash

frequency Cost: Free More information available at:

http://safetyperformance.org/resources/nchrp-17-38

http://www.hisafe.org/

http://safetyperformance.org/resources/nchrp-17-38

HSM Tools

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IHSDM – HSM Predictive Method Estimates a design's expected safety and operational performance Includes 6 Modules

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

Requires detailed design inputs Sensitive to subtle design elements across roadway segments Cost: Free More information available at:

http://www.fhwa.dot.gov/research/tfhrc/projects/safety/comprehensive/ihsdm/index.cfm

Updates made Consistent with the HSM Part C and Supplemental Chapters

Additional Features (Not Related to the HSM)



Agenda

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The Future

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HSM 2nd Edition Effort to produce HSM, 2nd Edition currently in-progress Targeted publication of 2020

Fixing America's Surface Transportation (FAST) Act Continued emphasis on safety Increasing prominence of performance-based decision-making

Caltrans Transportation Analysis Guide (TAG) On-going effort continuing through 2016 Incorporating HSM methods as part of overall update to transportation

analysis Also working to incorporate useful surrogates for safety where broader

research is lacking (e.g., pedestrian and bicycle safety)

Questions?

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Contact Information Matt Braughton

[email protected] 916.822.5351 (direct)

making the most of the highway safety...

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