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Creating a Critical Crash Rate Report Using Existing Tools and Available Information

Creating a Critical Crash Rate Report Using Existing Tools and Available Information. 2/19/08. Heath Hoftiezer, P.E., P.T.O.E Civil Engineer/ P.E. (Traffic) City of Sioux Falls. WHY ?. Outliers. Average Crash Rate. Statistical Theory. Calculating Crash Rates. Intersection Rates.

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Creating a Critical Crash Rate Report Using Existing Tools and Available Information

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  1. Creating a Critical Crash Rate Report Using Existing Tools and Available Information 2/19/08 Heath Hoftiezer, P.E., P.T.O.E Civil Engineer/ P.E. (Traffic) City of Sioux Falls

  2. WHY ?

  3. Outliers Average Crash Rate Statistical Theory

  4. Calculating Crash Rates Intersection Rates (number of crashes) * (1 million) Rate per Million Entering Vehicles = (number of years) * (ADT) * (365) Segment Rates (number of crashes) * (1 million) Rate per Million Vehicle Miles = (segment length) * (number of years) * (ADT) * (365) To calculate an average crash rate use the total number of all crashes for the intersections or segments that the average is desired for along with the total ADT of all intersections or segments and if applicable the total of all segment lengths

  5. Ra 0.5 Rc = Ra + k * ( )2 - m m 365 365 (ADT) * ( ) , For intersections (ADT) * ( ) * length , For segments 1000000 1000000 Calculating Critical Crash Rates Rc = Critical Crash Rate Ra = Average Crash Rate m = Vehicle Exposure During Study Period k = Constant based on Level of Confidence

  6. k and the Level of Confidence Level of Confidence 0.9950.9500.900 k 2.5761.6451.282

  7. Intersection Categories Type of Control Volume of Traffic Intersection Geometry

  8. Categories Currently Used in Sioux Falls • Signalized Intersections • Both roads have an ADT of over 10,000 Category I Category II Signalized Intersections One road has an ADT of over 10,000 Category III Signalized Intersections Both roads have an ADT of under 10,000

  9. Category IV Un-signalized Intersections Both roads have an ADT of over 4,000 • Un-signalized Intersections • One road has an ADT of over 4,000 Category V Category VI Un-signalized Intersections One road has an ADT of over 1,000 Category VII Un-signalized Intersections Both roads have an ADT of under 1,000

  10. Existing Tools Used Microsoft Access Microsoft Excel Internet

  11. Gathering Needed Information from the Internet ftp://ftp.state.sd.us/DPS/data_sharing/ IntersectionsState.mdb DPS_accident_sharing.mdb DPS_accident_sharing_ab.mdb

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