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NC Local Safety Partnership

NC Local Safety Partnership. Understanding Crash Data. Workshop Roadmap. . Module Objective. Understand crash data basics and characteristics of good quality data Understand what crash severity is and why it matters Learn what sources of crash data are available

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NC Local Safety Partnership

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  1. NC Local Safety Partnership Understanding Crash Data

  2. Workshop Roadmap

  3. Module Objective Understand crash data basics and characteristics of good quality data Understand what crash severity is and why it matters Learn what sources of crash data are available Understand how crashes are located to a specific spot on the road

  4. Module 2 – Crash Data Basic information on crash data

  5. Contributing Factors

  6. Haddon Matrix

  7. Haddon Matrix(example: Rear End Crash)

  8. The “Torturous Path” of Crash Data Collection Crash Occurs Crash Report Completed – DMV 349 Form Data Recorded in NCDMV Database Crash Data Transferred to State Database Data Analyzed and Disseminated

  9. Crash Data Quality What are some characteristics of high quality crash data?

  10. Crash Data Quality NHTSA “SIX PACK” Timeliness Accuracy Completeness Uniformity (or consistency) Integration Accessibility

  11. Crash Data Quality Strive for good quality data, but don’t let imperfect data hold you back! Road safety concerns can be addressed with the current data and tools on hand.

  12. Module 2 – Crash Data Crash Severity

  13. K A B K crash C O Deaths (which must occur within 12 months after the crash) resulting from injuries sustained in a specific road vehicle crash.

  14. K A B A crash C O Incapacitating injury– Injury obviously serious enough to prevent the person injured from performing their normal activities for at least one day beyond the day of the crash. Massive loss of blood, broken bone, unconsciousness of more than momentary duration are examples.

  15. K A B B crash C O Non-incapacitating evident injury - Obvious injury, other than killed or disabling, which is evident at the scene, but would not necessarily prevent the person from carrying on their normal activities. Bruises, swelling, limping, soreness are examples.

  16. K A B C crash C O Possible injury - No visible injury, but person complains of pain or has been momentarily unconscious.

  17. K A B O crash C O No injuries, but reportable property damage resulted from crash

  18. Crash Level Severity • Persons involved in the crash may suffer various levels of injury • Most severe injury controls “crash level” severity • Example: • One A injury, two B injuries, and one C injury • Crash level severity is “A” • Useful for tracking the trends of the most severe crashes

  19. Discussion • Why consider crash severity when addressing problem sites? • Higher severity indicates higher priority of location in addressing safety problem • Crash severity affects “cost” of crash • Fatal Crash = $4,600,000 • A Injury Crash = $270,000 • B Injury Crash = $80,000 • C Injury Crash = $40,000 • Property Damage only Crash = $5,400

  20. Discussion • Communicate with law enforcement to establish consistency and show value of data • Inspect crash reports of interest to verify severity and other information How can accuracy of crash severity data be improved?

  21. Module 2 – Crash Data Sources of Crash Data

  22. Sources of Crash Data What characteristics must a crash have to be a “reportable” crash?

  23. Sources of Crash Data • A reportable crash is a crash where: • A fatality occurred • A non-fatal injury occurred • Property damage of at least $1,000 occurred • A seized vehicle was damaged (any amount) • Location: Occurred on a trafficway (any land way open to the public for moving persons or property from one place to another) or occurred after the motor vehicle runs off the roadway but before events are stabilized

  24. Sources of Crash Data • Local level source – police crash reports • May be paper or electronic • State level source – NCDOT Traffic Engineering Accident Analysis System (TEAAS) • Electronic database of crashes on state or local roads

  25. Sources of Crash Data • Each year there are approximately 225,000 reportable crashes added to TEAAS • There is approximately a 30-day backlog in the manual data entry of crash data, and approximately a 1 week backlog for electronically submitted data (TRaCS, etc.) • TEAAS contains information on all reported crashes in North Carolina since January 1, 1990

  26. Sources of Crash Data • There are 3 levels of crash data in TEAAS: • Crash level - data specific to the crash regardless of units or persons involved (such as location, time of day, weather conditions, etc.) • Unit level - data specific to each individual unit regardless of the persons in that unit (such as speed, vehicle type, vehicle maneuver, etc.) • Person level - data specific to each individual (such as age, race, gender, injury, driver address, etc.)

  27. Module 2 – Crash Data Locating Crashes

  28. Locating Crashes Location is critical for determining areas of concern Crashes can be located via milepost (linear referencing) or coordinates (spatial referencing)

  29. Mileposts • Specify a location along a roadway (measured in miles) • Imaginary distance markers that follow the contour of the roadway • They are specific to each county and route MP 1.2 MP 1.22 MP 2.1

  30. Mileposts • Each route has defined “beginning” and “ending” points • Beginning milepost is usually 0.000 and ending milepost is usually equal to the total length of the route (added to the beginning milepost) • Some local routes (i.e. Main Street) that occur several times in the same county will start with different beginning mileposts • Feature mileposts are usually rounded to the nearest thousandths of a mile (three decimals)

  31. Mileposts • Mileposts allow for locating crashes on a roadway in relation to the features (intersections, boundaries, etc.) on that roadway • Location information from crash reports are used to calculate milepost values for crashes

  32. Crash Mileposting Information • Crashes are mileposted (located) using location information on DMV-349 crash reports • Location Information used: • Road On - Road name or route where the crash occurred • From Road - road name or route of an intersecting road near the crash • Distance From - Distance between crash and From Road • Direction From - Direction of crash from the From Road • Towards Road - Next intersecting road in the Direction from the From Road

  33. Crash Location Visualization • Example below could be described as: • Road On –Capital Blvd • From Road –Best St • Distance From –400 ft • Direction From – East • Towards Road –Green Rd

  34. Crash Location Visualization • Example below could be described as: • Road On –Capital Blvd • From Road – Green Rd • Distance From – 600 ft • Direction From – West • Towards Road – Best St

  35. Crash Mileposting Example 1.32 1.05 1.25 1.13 • The example crash would be mileposted as follows: • The crash occurred 400 feet (or 0.08 miles) east of Best Street (MP 1.05), so the milepost is calculated to be 1.05 + 0.08 = 1.13

  36. Crash Mileposting Exercise A 0.27 B 1.65 What are the mileposts for the following crashes? CrashOn RoadFrom RoadDist/DirFromToward Road A SR 9999 SR 1005 0.02 mi. East Pine Street B SR 9999 NC 55 0.08 mi. West SR 1667

  37. Geospatial Location 80°43'51.188"W 35°12'13.102"N Some agencies (e.g., Charlotte) use spatial locations for crashes

  38. Geospatial Location • Advantages • Greater potential precision • Independent of milepost shifting • Spatial analysis (e.g., hotspots) • Disadvantages • Requires significant manual effort • If police assign coordinates, accuracy is an issue (i.e., many crashes “occurring” at police station)

  39. Take Away Messages Crashes are random events with a variety of contributing factors Quality crash data is important – but don’t let imperfect data hold you back Crash severity levels are important and can impact decision making Data available from a variety of sources in various formats Different systems are used to locate crashes along a road

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