GIS for Transportation: Principles, Data and Applications

6.5 Next Week's Webinar



Next week, our guest speaker will be Mr. Jeff Roecker. Jeff graduated from Penn State with a degree in Geography and joined PennDOT in 2008. Jeff plays a lead role in the Department's Crash Data Analysis and Retrieval Tool (CDART), and he is the project manager for PennDOT's Strategic Highway Safety Plan (SHSP).

Crash Data Collection

FHWA requires all states to maintain a database of crashes in order to support the analysis of crash locations. There is variation from state to state on how they define reportable crashes, how they collect the information and how readily they share the information. Many states publish annual summaries of crash data for the prior year and also provide trending information for various crash statistics. The Pennsylvania Department of Transportation (PennDOT) publishes an annual report entitled Crash Facts and Statistics. The 2015 version of this publication can be found here.

Crash data is important to state DOTs for a number of reasons. First, without this data, an agency doesn’t know if things are improving. Second, this data can offer clues to where safety improvement or countermeasures are most needed. Crash patterns can also be used to help law enforcement design initiatives associated with seat belt usage and checkpoints for impaired drivers.

Law enforcement officials are generally responsible for reporting crashes. In Pennsylvania, the Commonwealth of Pennsylvania Police Officers Crash Report Manual provides law enforcement agencies instructions on reporting crash data including definitions of which types of crashes are reportable to PennDOT. The police use a multipage form (AA 500) to report crash data. The form captures extensive information about the crash including the location, all vehicles and individuals involved in the crash, the number and nature of any injuries, weather and road conditions at the time of the crash, a diagram of the crash and statements from any witnesses. PennDOT also provides a detailed reference document for completing the form.

PennDOT also has a web based system called the Crash Reporting System (CRS) which provides an electronic alternative to submitting crash data. A user’s guide for the system can be found here. CRS is also used by PennDOT to review and validate all data which is automatically retrieved from paper forms which are received from law enforcement agencies. Any meaningful analysis of crash data requires that the data is accurate and complete.

Crash Analysis

State DOTs use crash data to identify locations where there are unusually high crash rates and also to determine measures which will likely lower these crash rates. One of the most useful types of crash analysis, which is used by many state DOTs, is a spatial technique known as cluster or hot spot determination. This type of determination is done using GIS software by stepping along each route and identifying sections of roadway which meet the definition of a crash cluster based on established parameter settings for the analysis.

In Pennsylvania, crash data submitted by law enforcement agencies electronically via CRS or the AA500 paper form, are processed and stored in a system known as the Crash Data Access and Retrieval Tool (CDART). CDART is a geospatial application which allows PennDOT to perform a variety of crash analyses including crash cluster analyses. It performs two basic types of crash cluster analysis. The first is a standard cluster analysis where each road is considered separately. The second is an intersection based cluster which examines the number of crashes which occur on all associated roads within a certain distance of the point of intersection. One of the other interesting analyses CDART performs is a “before and after” analysis which compares crash frequencies for a section of roadway before and after a safety improvement was implemented to determine its effectiveness. For each of the analyses CDART performs, the system allows the user to generate tabular or map based outputs. CDART is an internal tool to PennDOT and is not available for public use.

On May 30, 2013, Sharon Hawkins of the Arkansas DOT gave a 42-minute presentation on some of the GIS tools they use to locate and analyze crashes. The presentation was part of the FHWA GIS in Transportation webinar series. The webinar provides an excellent perspective on the importance of GIS in collecting and analyzing crash data. Many states have gone through a similar evolution and set of problems in their efforts to manage and utilize crash data to improve highway safety.

Assignment 6-6 (10 points)

Review the Pennsylvania Police Crash Reporting form and associated guidance for reporting crashes and watch the Arkansas DOT’s May 2013 webinar on GIS tools they’ve used to locate crashes and analyze crash data. Address the questions listed below and submit your responses as an M.S. Word document to Assignment 6-6 in Canvas.

  1. How does Pennsylvania define a reportable crash? (1 point)
  2. What are some types of information a police officer can provide to locate a crash in Pennsylvania? (2 points)
  3. Why is it important for PennDOT (or any state DOT) to ultimately associate a crash with a specific location along a roadway as opposed to simply capturing the coordinates of the crash? (2 points)
  4. In Arkansas’s evolution of locating crashes, they deployed GPS units to the police to help them accurately locate a crash. What was one of the problems they identified after providing these units to the police? (1 point)
  5. What are some of the GIS tools Arkansas DOT has rolled out to help law enforcement locate crashes? (2 points)
  6. How does Arkansas DOT benefit from law enforcement’s ability to more accurately locate crashes? (2 points)

Assignment 6-7 (5 points)

After reviewing the background material for next week’s webinar and the biography for next week’s speaker, come up with 3-5 questions which are clearly stated and are relevant to the webinar topics. Submit the questions to Assignment 6-7 in Canvas.

Webinar Questions Rubric (5 points)
Criteria Ratings Points
Question Quality
Excellent: Questions were clearly worded, demonstrated a thorough review of the background material and thoughtful reflection and insight on the part of the student.
5.0 pts
Satisfactory: Questions were somewhat clear, demonstrated some review of the background material and some reflection and insight on the part of the student.
3.0 pts
Poor: Questions were unclear and/or demonstrated little or no review of the background material and/or demonstrated little or no reflection and insight on the part of the student.
1.0 pts
5.0 pts
Total Points: 5.0