translation of linear-reference crash data to on-street/cross- street nomenclature
TRANSCRIPT
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
21,812DOT RECORDS99 & 00 ONLY
58,887DHSMV Records
1999 – 2001
103,298 Hillsborough County and COT Crash
Records
1999 - 2001
Crash Data Universe
What is Linear-Referencing Roadway Section IDs
– Section ID Comprised of three non-unique sets of data• County ID aa• 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: 10.687 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
CriteriaLinear
ReferenceOn Street /
Cross Street Note
Statewide Applicability
Compatible With Existing Local Data
Intersection Analysis
Mid-Block Analysis
Spatial AccuracyHillsborough County Has a Highly Accurate Centerline Layer
Cross Reference to Roadway Attributes
Ease of Use On Scene
Pros and Cons
Two FeaturesDrawn to Represent
Single Event
Locating Crashes in GIS using Linear Reference Mileposts
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 OneRelationship
Pros and Cons
Propagated Spatial Error
Pros and Cons
Local CenterlineRemoves “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
