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Evaluation Of The Locations Of Kentucky’s Traffic Crash Data

Evaluation Of The Locations Of Kentucky’s Traffic Crash Data. Eric Green, GISP, MSCE , PE. Background. Safe , Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU )

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Evaluation Of The Locations Of Kentucky’s Traffic Crash Data

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  1. Evaluation Of The Locations Of Kentucky’s Traffic Crash Data Eric Green, GISP, MSCE, PE

  2. Background • Safe, Accountable, Flexible, Efficient Transportation Equity Act: A Legacy for Users (SAFETEA-LU) • Traffic Safety Information System Improvement Grants available to states under section 408 of the bill • Follow-up to 2004 study: • "Evaluation of the Accuracy of GPS as a Method of Locating Traffic Collisions" • Accurate crash locations: • Crash rates, highway improvement, education and enforcement efforts

  3. Outline • Methods for locating a crash for a Kentucky police officer • Review of a random sample of crash data • Analysis of current location data • Where should a crash be located? • Conclusions / Recommendations

  4. Paper Reports • Submitted manually • GPS from Magellan, Google® Maps, 911 system • County, Route and Milepoint (CRMP) using reference system

  5. eCrash KYOPS • MapIt • Added October 1st 2007 • CRMP data linked to GPS • Between/Intersect streets • Searchable • RT Unique: “034-US-0068 -000”

  6. Previous Report • Crash data from January to June of 2003 • Lat/Long added in 2000, required June 1st, 2002 • Accuracy by County, Route and Milepoint (CRMP) • Linear reference system • 55% correct • Accuracy by GPS • Using Magellan SporTrak handheld unit • 58% correct

  7. Random Sample • 222 random crashes from 2009 were reviewed • All had Lat/Long generated by the MapIt system • This was considered the reported location • The actual location was derived from: • Report narratives • Addresses • Intersecting or between roads • The accuracy of each location was classified: • YES – within 500 feet of actual location • NO – outside of 500 feet from actual location • UNKNOWN – unable to determine actual location

  8. Random Sample • Each report was classified as: • Intersection • Between Streets • None • 500 feet is useful for network screening but more accurate locations are preferred for individual crash analysis • A range was given for each crash indicating accuracy of each presumed locations • Definitive locations such as addresses had small or ranges of zero • Larger ranges were used when the location was determined to be between two reference points

  9. Random Sample Results

  10. Random Sample Results • If the unknown locations were removed • 152 of the 167 or 92% were accurate • 92% can be compared to a similar study conducted 6 years ago which yielded: • 58% were correct by Lat/Long • 55% were correct by CRMP

  11. Crashes Coded as Inaccurate • Lat/Long is not consistent with address/reference (12 crashes) • No reference point (1 crash) • These could be a result of the officer needing to "guess" where to click on the mapping system • Additional reference systems could help minimize this error

  12. Crash Database Analysis • Latest data containing the MapIt-based location • October 1st, 2007 to December 31st, 2009 • 334,354 crashes • Data were plotted using CRMP data • Lat/Long data was assigned to all plotted CRMP crashes • The distance between the Lat/Long location and the CRMP location was calculated

  13. Crash Data Potted by Lat/Long

  14. Crash Data plotted by Lat/Long Showing County Check

  15. Crash Data by Year and County Check *2007 only represents 3 months of the year

  16. Average Distance by Year (Usable) *2007 only represents 3 months of the year

  17. Most Egregious Errors • The crash database was sorted by distance and several of the most egregious errors were examined • There were two types of electronic reporting errors that yielded large distance between the CRMP and Lat/Long locations • Lat/Long Glitch • ‘Distance From’ Glitch

  18. Lat/Long Glitch • For several crashes one of the Lat/Long coordinates was off by -96 degrees • Adding this value to these crashes plotted the crash very close to the CRMP location • MFN of 70651040 • reported longitude of 7.759983063 • longitude based on the CRMP of -88.2399139 • 7.76 - 96 = -88.24 • The data base actually showed “07.759983-01” • This was only observed in 252 crashes, most of which were in 2008 • The error was not observed since January of 2009. It is assumed to have been fixed.

  19. ‘Distance From’ Glitch • This error was harder to quantify its frequency as the distance was not nearly as egregious • It was noticed in about 700 crashes (presumed to be many more) • The GPS coordinates were modified by the ‘distance from’ field • The office should not need to use the ‘distance from’ field when using the MapIt system (it is used for CRMP) • This error is currently repeatable • Perhaps by design, but it was never noticed to be deliberate

  20. Paper Report Errors • Several of these errors were related to the officer entering the data wrong or the data being keyed into the system incorrectly • There were 731 crashes with a Lat/Long minute value 60 or greater • Over 400 crashes with noticeably bad Lat/Long • Several crashes that had no minutes or seconds or suspicious values such as 30 minutes • Although these represent a small number of crashes, they are a much higher proportion when only paper reports (about 27,000) are considered

  21. Adding A County Check • If all crashes that were plotted outside of their reported county are removed, this distance reduces from 3.8 to 0.2 miles • This implies that if a county check was performed before accepting a crash that the most egregious errors could be eliminated • Most of the worst errors occurred prior to 2009 • The average distance in 2009 would reduce from 0.3 miles to 0.1 miles by requiring this check • There is a county bounding box check although it must not be required

  22. Unexpected Error - Unmodified MapIt • Crashes indicating that the officer used the MapIt system and did not edit its location • It would be expected that the distance between the CRMP and the Lat/Long locations would be ostensibly zero • It would be expected to observe rounding and map projection errors that would yield some distance between the two locations • Unexpectedly, however, there were 5,267 (4.4%) usable crashes in 2009 that used an unedited MapIt location, yet had a distance of 500 feet or more

  23. Unmodified MapIt Error • 6 crashes with a distance over 4,000 miles (explained by the Lat/Long Glitch discussed earlier) • There were 12 crashes with a distance of over 20 miles • The average distance of this dataset was 6.6 miles (1.3 miles excluding the 6 with latitude/longitude errors) • Several of these crashes were reviewed to determine the reason for these errors • For 127of the crashes the error seemed to be related to ‘distance from’ error discussed above.

  24. Crash report# 70766928 – Covington Police Department, 10/22/2009

  25. Crash report# 70766928 - Covington Police Department, 10/22/2009

  26. Crash report# 70766928 - Covington Police Department, 10/22/2009

  27. Unmodified MapIt Error Summary • A summary was performed by county-route combinations • A count of each county-route was compared to the count of that county-route’s occurrence in all 2009 crashes • A percentage was calculated based on these two counts • The unmodified MapIt location database represents 4.4% of all 2009 crashes • A percentage higher than 4.4% is overrepresented • Several county-routes had very high percentages implying that there may be something wrong with these routes in the MapIt database

  28. Unmodified MapIt Error by County-Route

  29. Analysis by Distance Between CRMP and GPS • Most of the location errors have been addressed and mitigated in KYOPS • Analyze paper reports or electronic reports with modified MapIt locations • The distance between the Lat/Long and CRMP should be zero for all unmodified MapIt • The averages were not driven down by the frequency of such crashes

  30. Properly Locating a Crash • Location of the first harmful event • Priority of roadways: • 1. Interstates* • 2. Parkways* • 3. US routes* • 4. KY routes* • 5. All other roads • Intersection and between used when available *The lower number should be used if both roads are the same priority

  31. Conclusions/Recommendations • 92% of all crashes were accurate compared to around 50% in the previous study • Most of this improvement can be attributed to the implementation of the MapIt system in eCrash • A large majority of incorrectly located were largely due to a lack of reference points • The MapIt system currently requires user to know where they are on a map • Identified errors should be investigated by KYOPS

  32. Potential Improvements • Aerial photos • Integrated GPS receivers • Reference log data • Mileposts, bridges, culverts, etc. • Training • QC of location data, state road preference (the importance) • Contact specific agencies or evaluate county data • ‘Distance From’ glitch • Edits to check for county and distance between CRMP and GPS

  33. Contact Information • Eric Green, M.S.C.E, P.E.Kentucky Transportation CenterResearch Engineer140C Raymond BuildingUniversity of KentuckyLexington, KY 40506-0281  egreen@engr.uky.eduPhone: (859) 257-2680 Toll Free: (800) 432-0719Fax: (859) 257-1815 www.ktc.uky.edu http://www.ktc.uky.edu/Reports/KTC_10_16_KSP3_10_1F.pdf

  34. Questions?

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