Data-Driven Safety Analysis - TEXAS STATE Driven Safety Analysis.pdf Data-Driven Safety Analysis...

Click here to load reader

  • date post

  • Category


  • view

  • download


Embed Size (px)

Transcript of Data-Driven Safety Analysis - TEXAS STATE Driven Safety Analysis.pdf Data-Driven Safety Analysis...

  • Data-Driven Safety Analysis

    Integrating Safety Performance into ALL Transportation Investment Decisions

  • What’s happening?


    • Shrinking budgets • Growing lists of needs • Increasing fatalities • Establishing Safety performance measures

    Credit: Bloomberg,

  • We need to know how a roadway will perform in terms of safety

    3 Source: Microsoft clip art, Wikipedia

  • What is DDSA? •The application of the latest evidence-based tools and approaches to safety analysis •Provides reliable estimates of an existing or proposed roadway’s expected safety performance •Helps agencies quantify the safety impacts of transportation decisions, similar to the way agencies quantify:

    – traffic growth – environmental impacts – traffic operations – pavement life – construction costs


    Source: AASHTO, AASHTOWare, Roadway Safety Foundation

  • Foundational DDSA Methods: the AASHTO Highway Safety Manual, first edition


    2010 Release: •Rural Two-Lane Roads •Multilane Rural Highways •Urban/Suburban Arterials

    2014 Supplement: •Freeway Segments •Ramps •Ramp Terminals

    Source: AASHTO

  • A Document Akin To the HCM…

    Definitive; represents quantitative ‘state-of- the-art’ information

    Widely accepted within professional practice of

    transportation engineering

    Science-based; updated regularly to

    reflect research

    1 2 3

    The Vision for the HSM

    6 Source: Transportation Research Board

  • The HSM has resulted in the development of:

    • Spreadsheets

    • Software Products

    • Guidance Documents

    • Crash Modification Factors Clearinghouse


  • An Illustration of DDSA…

    All three of these meet design standards…


    45 fatal and injury crashes/year 110 fatal & injury crashes/year 65 fatal & injury crashes/year

    Alt 2 Alt 1 No-Build

    but DDSA tells us they would perform very differently from a safety perspective.

    Source: CH2MHILL

  • The EDC Data-Driven Safety Analysis Initiative…

    Goal: Integrate safety performance into ALL transportation investment decisions

    9 Source: FHWA

  • Applying DDSA in Project Development Process


  • Where can DDSA be applied in the Project Development Process?

    Source: FHWA 11

  • DDSA in Planning 12

    Source: FHWA

  • DDSA in the Planning Process

    DDSA tools can be applied to help identify which roadways aren’t performing as they should, determine the scope and need of potential projects, and prioritize them.


  • DDSA in the Planning Process

    • System Level Planning • Network Screening

    • Project Level Planning • Establishing Project Scope • Project Prioritization


  • What is Network Screening?

    • i.e. Which sites have the most potential for safety improvement?

    Steps 1. Establish focus 2. Identify network 3. Select performance measures 4. Select screening method 5. Screen and evaluate results


  • Traditional vs. Advanced Network Screening From simple safety performance measures: • Crash frequency • Crash rate • Equivalent property damage only (EPDO) To advanced safety performance measures: • Excess Predicted Average Crash Frequency • Level of Service of Safety • Potential for Safety Improvement • Systemic Sites with Promise


  • 17

    Level of Service of Safety

    Tool: Agile Assets Safety Analyst

    Credit: Montana DOT

    Example: MT DOT - Network Screening

  • DDSA in Alternatives Analysis 18

    Source: FHWA

  • DDSA in Alternatives Analysis

    DDSA tools can predict the number and severity of crashes for each project alternative, allowing safety performance to be considered along with other project criteria.


  • Integrating Safety into NEPA Analysis

    20 Source: FHWA

    Po lic

    y/ St

    ak eh

    ol de

    r In

    vo lv

    em en


    Source: FHWA

  • When might a more-robust safety analysis in the environmental phase be appropriate?

    • When Safety is included in the Purpose and Need

    • Projects that claim a safety benefit

    • Projects where there could be a substantial difference in safety for the alternatives being considered

    • Projects with existing safety issues


  • Example: LA DOTD – EIS Alternatives Analysis

    I-12 to Bush, LA Four alternatives were considered to replace a two-lane, un-divided roadway with a four- lane, divided roadway with controlled access • All four alignments

    predicted a reduction in crashes from the No Build alternative

    Credit: Urban Systems, Inc. and Louisiana DOTD


  • Potential Reduction in Crashes, Costs

    Example: LA DOTD – EIS Alternatives Analysis

    Credit: Louisiana DOTD


  • Benefits from use of IHSDM • Quantify safety costs and benefits • Safety given equal weight in comparative


    Corps of Engineers selected Alternative Q, which had a predicted crash reduction of 6% and a $1.5M cost savings to society

    Example: LA DOTD – EIS Alternatives Analysis


  • DDSA in Design


    Source: FHWA

  • DDSA in the Design Process

    DDSA can be used to determine optimal design criteria, considering both safety and cost. • DDSA helps justify

    flexibility in design • design exceptions • performance-based

    practical design


  • 8-27

    Example: AZ DOT Analysis of Design Criteria

    Alternative Improvements Included: • Widening to 5 ft shoulders • Widening to 8 ft shoulders

    (MP 441 to 466)


    Credit: Arizona DOT

  • Plot of Geometric Features and Expected Crashes Example: AZ DOT Analysis of Design Criteria

    Credit: Arizona DOT


  • Crash Prediction Results Example: AZ DOT Analysis of Design Criteria

    Safety Analysis: • Model was un-calibrated as used (not necessary for

    comparative alternatives analysis) • Alternative B (8-ft shoulders) would reduce crashes

    by 4 percent more than Alternative A (5-ft shoulders)

    Credit: Arizona DOT


  • Example: AZ DOT Analysis of Design Criteria

    Economic analysis: • Although Alternative B (8-ft shoulders) could

    provide the greater benefit in reduction in fatal and injury crashes, Alternative A (5-ft shoulders) would provide the greater return on investment and was selected as the preferred alternative.

    Credit: Arizona DOT


  • Example: MN DOT – Communicating PBPD US Hwy 10 Access Study

    31 Source: Bolton & Menk Credit: Anoka County and Minnesota DOT

  • Example: MN DOT – Communicating PBPD US Hwy 10 Access Study

    32 Source: Bolton & Menk Credit: Anoka County and Minnesota DOT

  • Construction, Operations, and Maintenance

    Source: FHWA


  • DDSA in Construction, Operations, and Maintenance

    • Interstate Access Requests • Intersection Control

    Evaluation (ICE) • Traffic Impact Studies • Work Zones • Part-Time Shoulder Use • Performance Management


  • Performance Management

    Seven National Goals (MAP-21) • Safety • Infrastructure Condition • Congestion Reduction • System Reliability • Freight Mobility and Economic Vitality • Environmental Sustainability • Reduced Project Delivery Delays


  • State of Repair CRS Range

    9.0 to 7.6 Excellent 7.5 to 6.1 Good 6.0 to 4.6 Fair 4.5 to 1.0 Poor

    IRI Range (in/mi) 1 to 94 Good

    95 to 177 Fair > 177 Poor

    SRI Range Minimal Good

    Low Minor Medium Moderate

    High Severe 5% 5%

    Evaluating bridge and pavement condition data alongside safety performance to prioritize projects

    • Condition Rating System (CRS) – Structural: Loss of load carrying capacity or structural breakdown

    • International Roughness Index (IRI) – Functional/Surface: Excessive roughness impacti