Translation of Linear-Reference Crash Data to On-Street/Cross- Street Nomenclature

51,180 DHSMV in Local DBASE 7,707 DHSMV Not in Local DBASE 395 DOT Not in Either DBASE 4,403 DOT Not in DHSMV 19,398 DOT in Local Data 2,019 DOT Not in Local DBASE but in DHSMV 21,812 DOT RECORDS 99 & 00 ONLY 58,887 DHSMV Records 1999 – ,298 Hillsborough County and COT Crash Records Crash Data Universe

What is Linear-Referencing  Roadway Section IDs –Section ID Comprised of three non-unique sets of data County IDaa Section #bbb Subsection #ccc Forms Unique Roadway ID aabbbccc –Sections tend to follow State Road Numbers, but the relationship is not absolute  Mileposts –Three-digit precision ie: Miles –Used with Roadway Characteristics Inventory (RCI) to record the location of: Point Features/Events (Section – Milepost) Linear Features (Section – Beginning Milepost – Ending Milepost)

What is Linear-Referencing

On Street / Cross Street Crash Data  Uses Intersection, Intersection Influence, and Offset Information –N. Florida Ave and Polk Street –At the Intersection –(or) Influenced by Intersection – 50 ft South –(of) Not at the Intersection – 200 ft North  Geo-location Methodology –Assign Crash Event to Appropriate Intersection !!!) –Filter Mid-block Crashes by Query of Intersection Influence Attribute –Either Remove Mid-Block Crashes or Use GIS Script to “back crashes off of the intersection” Expletive Deleted

Pros and Cons

Two Features Drawn to Represent Single Event

Locating Crashes in GIS using Linear Reference Mileposts

 A Route is a GIS Feature that has: –Common ID Attribute (Roadway ID aa.bbb.ccc) –XY coordinates –Geographic Length Attribute –M (measure) Attribute  A Route Event Theme is: –A table of Events such as Crashes, Point Attributes, Linear Attributes –Each Event Has Roadway ID Attribute Milepost Attribute (or Beginning and Ending MP info)

Associating Route Events with Underlying Point Features  ArcGIS 8.x ArcTool Box “Nearest Node” Tool –Associate a Point Feature from one Coverage with the nearest Node in another coverage  Error Trapping –Check if all State Road Intersections are assigned Local Centerline Intersection Ids –Check if all Local Intersections within a buffer of State Routes are assigned a Section and Milepost # –Manually Review all Interchanges and Areas of Complex Geometry

Pros and Cons Difficult Many to One Relationship

Pros and Cons Propagated Spatial Error

Pros and Cons Local Centerline Removes “Doglegs”

Associating Crash Data with Intersections  “Jump” Crash Event to Nearest DOT Intersection Feature  Store the Offset Distance  Transfer DOT Crash to Associated Local Centerline Intersection  Use Crash Offset Script to relocate crash to correct position using local centerline Geometry

Contact Info: Demian Miller Tindale Oliver & Assoc. Tampa, FL