SPR 667 – Assessment of Statewide Intersection Safety Performance
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SPR 667 – Assessment of Statewide Intersection Safety Performance. TAC Meeting August 31, 2009 2:00-3:30PM. Agenda. Meeting Objectives. Research Objectives. To quantify the safety performance of typical intersections  

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Spr 667 assessment of statewide intersection safety performance

SPR 667 – Assessment of Statewide Intersection Safety Performance

TAC Meeting August 31, 2009 2:00-3:30PM


Agenda

Agenda


Meeting objectives

Meeting Objectives


Research objectives

Research Objectives

  • To quantify the safety performance of typical intersections  

    • To assemble a statewide inventory of intersections including location, geometry, control and volume data.

    • To characterize by a variety of geometric, operational, and volume features the safety performance of typical intersections.

      • This performance will include both statistical summaries and exploration of the applicability of predictive models.


Review of tasks

Review of Tasks

  • Project Initiation – complete

  • Literature Review – complete

  • Data Assembly & Research Design – 90% complete

  • Pilot Study – 85% complete

  • Full Intersection Study – 20% complete

  • Summary Data Analysis – 20% complete

  • Develop Safety Performance Functions

  • Final Report

    Budget: $122,516

    Encumbered: $42,086 (34%)

    Balance: $80,430


Background

Background

  • Nearly 21% U.S. fatalities were identified as intersection or intersection-related (2007)

  • ITE estimates 50% of all reported crashes occurred at intersections

    • 55% of injury crashes

    • 48% of property-damage crashes.

  • Oregon (2007) intersection crashes accounted for 38% of total

    • 18% of fatal crashes

    • 39% of injury crashes


Literature review

Literature Review

  • PART 1

    • A summary of individual geometric, operation, traffic control, and other features

  • PART 2

    • Statistical summaries

    • Methods for pattern diagnostics

    • Modeling the safety performance at intersections.


Part 1 sources for intersection elements

PART 1Sources for Intersection Elements

  • Harwood et al. “Safety Effectiveness of Intersection Left- and Right- Turn Lanes”

  • Model Minimum Inventory of Roadway Elements (MMIRE)

  • Highway Safety Manual (HSM) Draft 3.1

  • Elvik and Vaa “Handbook of Road Safety Measures”

  • Other research

  • List is not exhaustive


Part 2 statistical summaries crash rates

PART 2Statistical Summaries (Crash Rates)


Spr 667 assessment of statewide intersection safety performance

Functional class

District or region


Part 2 statistical summaries

PART 2Statistical Summaries


Part 2 pattern diagnostics and proportions

PART 2 Pattern Diagnostics and Proportions

  • Excess proportions

    • HSM/Safety Analyst

  • Direct diagnostics

    • Comparisons of individual crash type proportions to all others


Part 2 safety prediction methods

PART 2 Safety Prediction Methods

  • Regression models

    • Negative Binomial models

    • Tree-based regression

    • Probit models

  • Urban – rural

  • Intersection type

  • Severity or crash type

  • Volumes significant in all models


Literature review conclusions

Literature Review Conclusions

  • Identified a long list of potential intersection elements

  • Crash rates varied considerably from state-to-state

  • Most summaries aggregated at relatively high level

  • Interestingly, all summaries used total crashes and did not develop separate injury rates or rates by any other crash category or causation.

    • Roundabouts were not included as separate category

    • Pedestrian or bicycle elements were also absent.

  • All of the summaries are “snapshots” in time and do not appear to routinely updated.


Literature review conclusions1

Literature Review Conclusions

  • Summarizing the crash data in terms of typical diagnostics appears to be very valuable effort.

  • Data requirements for predictive models are significant and a primary reason why there has been limited development.

  • The relationship of intersection characteristics with crash frequency, crash severity, and particular crash types is complex.

  • In nearly every model, volumes were a significant variable.


Data assembly

Data Assembly

  • ODOT CAR Code Setup Book

    • State highway system intersections (9,139)

    • Other system (143,186)

  • ODOT Crash Data System (via OrTSDA)

  • ODOT Digital Video Log (DVL)

  • ODOT Integrated Transportation Information System (ITIS)

  • Google Earth / GIS Files

  • Counts

    • Traffic counting firms

    • City/County Engineering & Planning Offices

    • PORTAL, Google Traffic


Intersection crash data

Intersection Crash Data

  • State Highway

    • Highway and milepost

  • City

    • Intersecting street numbers

  • County

    • Either mileposted or intersecting street numbers

Intersection

Possible

Intersection-related


Odot car code setup book

ODOT CAR Code Setup Book


Car setup book

CAR Setup Book

Remaining records “NULL” traffic control


Pilot study

Pilot Study

  • Objectives

    • Test data collection strategies

    • Define feasible data elements

    • Estimate effort

    • Help formulate likely data distributions

    • Test crash data scripts and summaries

  • All data elements

    • 49 NCHRP Flashing Yellow Arrow Intersections

    • 55 HSM Calibration Project Intersections

  • Partial data elements

    • 244 State highway–state highway intersections


Google earth map of intersections

Google Earth Map of Intersections


Data collection form

Data Collection Form


Data collection google earth

Data Collection: Google Earth

Google Earth can provide an aerial view of:

-Intersection Type-Turning Lanes

-Parking

-Channelization

-Lat/Long Coord.

-Urban/Rural

-Bicycle Facilities

-Ped. Facilities

-Measurements

-Length, Width


Data collection

Data Collection

  • Resolution is an issue in rural areas when making measurements.

John Day:

US 26 (005) and US 395 (048)


Digital video log

Digital Video Log

  • ODOT’s Digital Video Log provides street level views which can be used to identify:

    • Signalization-Intersections (ex: S = 3 = S)

    • # of Turning Legs-Medians and Channelization


Aadts from jurisdictions

AADTs from Jurisdictions


Counts from traffic firms

Counts from Traffic Firms


Variable summary n 104

Variable Summary (N=104)


Variable summary n 1041

Variable Summary (N=104)


Crash frequency n 347

Crash Frequency (N=347)

DRAFT-DRAFT – DRAFT – DRAFT- DRAFT - DRAFT


Crash rates n 254

Crash Rates (N=254)

DRAFT-DRAFT – DRAFT – DRAFT- DRAFT - DRAFT


Crash patterns

Crash Patterns

DRAFT-DRAFT – DRAFT – DRAFT- DRAFT - DRAFT


Crash patterns by vehicle movement

Crash Patterns By Vehicle Movement


Draft results from pilot study

Draft Results from Pilot Study

  • Many elements probably not needed for summaries / patterns

  • Crash script developed

    • Refining / testing in Access database

    • Quality control checks needed

  • Traffic volumes

    • Hardest to get (off state system)

    • Time challenge (year of data collection)

    • Still some other avenues to pursue

  • Signal timing

  • Need to study appropriate aggregations


Work plan deliverables

Work Plan Deliverables

  • 1 - Literature review

  • 2 - Brief memo to TAC summarizing findings, progress, and recommendations for pilot study intersections and scope

  • 3 - Interim report summarizing findings of the pilot study, progress, and recommendations for full field study. Preview of statistical summaries that will be conducted.

  • 4 - Interim report summarizing the results summary data analysis

  • 5 - Final report


Revised work plan

Revised Work Plan

  • Discussion


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