Mapping Accident Data and Use of GIS Applications Jeff Kaufman, AICP Transportation Safety Coordinator Houston-Galveston Area Council Houston, TX April 19, 2007

The Unwieldiness of Crash Data  Texas Department of Public Safety Crash Data Code Guide – 65 pages of codes  Four years of data – 330,000 records  310 columns/fields per record  Over 100 million pieces of information!

Benefits of a GIS-based Crash Database  Ability to choose specific locations of interest  Ability to query like a database  Ability to manipulate data  Ability to tie data in to other areas of study  On-the-fly mapping for presentations  “A picture speaks a thousand words”

Creating a GIS-based Crash Database Crash Data w/Locations Base Map with Road Names

1.Crash reporting errors in geographical identifiers 2.Recording errors 3.Base map errors 4.Unresolvable errors Issues with Creating a Crash System Database

Ned Levine, PhD Karl Kim, PhD

Data Cleaning Program Convert Field Names into Base Map Street Names IF CITY = '07905' AND MAINSTRT = '1STCO' THEN MSTREET = 'FIRST_COLONY BLVD'; IF CITY = '07905' AND MAINSTRT = '6TH' THEN MSTREET = '6TH ST'; IF CITY = '07905' AND MAINSTRT = 'AIRP' THEN MSTREET = 'AIRPORT'; IF CITY = '07905' AND MAINSTRT = 'ALST' THEN MSTREET = 'ALSTON'; IF CITY = '07905' AND MAINSTRT = 'ARCAD' THEN MSTREET = 'ARCADIA DR'; IF CITY = '07905' AND MAINSTRT = 'AUST' THEN MSTREET = 'AUSTIN'; IF CITY = '07905' AND MAINSTRT = 'ANSTO' THEN MSTREET = 'ANSTON'; IF CITY = '07905' AND MAINSTRT = 'AUTUM' THEN MSTREET = 'AUTUMN RIDGE DR'; IF CITY = '07905' AND MAINSTRT = 'AVEE' THEN MSTREET = 'AVE_E'; IF CITY = '07905' AND MAINSTRT = 'ALKIR' THEN MSTREET = 'ALKIRE LAKE DR'; IF CITY = '07905' AND MAINSTRT = 'AIRPO' THEN MSTREET = 'AIRPORT'; IF CITY = '07905' AND MAINSTRT = 'AVEE' THEN MSTREET = 'AVE_E'; etc.

IF RSTREET = ‘8’ THEN RSTREET = ‘BW 8’; IF RSTREET = ‘BELTWAY’ THEN RSTREET = ‘BW 8’; IF RSTREET = ‘BELTWAY 8’ THEN RSTREET = ‘BW 8’; IF RSTREET = ‘KATY FREEWAY’ THEN RSTREET = ‘IH 10 W’; IF RSTREET = ‘KATY FWY’ THEN RSTREET = ‘IH 10 W’; IF RSTREET = ‘KATY’ THEN RSTREET = ‘IH 10 W’; IF RSTREET = ‘GULF FREEWAY’ THEN RSTREET = ‘IH 45 S’; IF RSTREET = ‘GULF FWY’ THEN RSTREET = ‘IH 45 S’; IF RSTREET = ‘GULF’ THEN RSTREET = ‘IH 45 S’; etc. Pre-processing Program – I Standardize Freeway Names

IF RSTREET = 'FIRST ST' THEN RSTREET = '1ST ST'; IF RSTREET = 'SECOND ST' THEN RSTREET = '2ND ST'; IF RSTREET = 'THIRD ST' THEN RSTREET = '3RD ST'; IF RSTREET = 'FOURTH ST' THEN RSTREET = '4TH ST'; IF RSTREET = 'FIFTH ST' THEN RSTREET = '5TH ST'; IF RSTREET = 'SIXTH ST' THEN RSTREET = '6TH ST'; IF RSTREET = 'SEVENTH ST' THEN RSTREET = '7TH ST'; IF RSTREET = 'EIGHTH ST' THEN RSTREET = '8TH ST'; IF RSTREET = 'NINTH ST' THEN RSTREET = '9TH ST'; etc. IF MSTREET='A' THEN MSTREET='AVE_A'; IF MSTREET='B' THEN MSTREET='AVE_B'; IF MSTREET='C' THEN MSTREET='AVE_C'; IF MSTREET='D' THEN MSTREET='AVE_D'; IF MSTREET='E' THEN MSTREET='AVE_E'; IF MSTREET='F' THEN MSTREET='AVE_F'; IF MSTREET='G' THEN MSTREET='AVE_G'; etc. Pre-processing Program – II Standardize Numeric and Lettered Street Names

1.Correcting street name inconsistencies 2.Correcting geographic errors (e.g., adding new streets; creating intersections that don’t intersect) 3.Creating pseudo-intersections for place locations (e.g., freeway exit locations; cul-de-sacs that don’t intersect; places) Modifying the Base Map

1. Comprehensiveness (‘match rate’) 2. Geocoding accuracy (correct placement) 3. Spatial accuracy (resolution) Goal: 90% matching w/90% accuracy Three Criteria for Geocoding

Analysis Types  Crash numbers (volumes)  Crash risk  Hot spots

Crash Numbers  Quantification  Resolution of information  Aggregation of Data for clearer picture  CrimeStat® Spatial Statistics Program –

Crash Risk  Definition: Crashes per 100 million Vehicle Miles Traveled (VMT) Analysis Approaches:  Crash Risk by City/County/Region  Crash Risk by Road Type  Crash Risk by Mode of Travel  Etc.

Serious Crash Risk (Serious Crashes per 100 Million VMT) Jurisdictional Comparisons CityCrash Risk Pearland378 Galveston337 Baytown334 Rosenberg320 Pasadena290 Conroe247 Houston231 Texas City211 Sugar Land192 Houston Region204 State of Texas149

Serious Crash Risk Serious Crashes Per 100 Million VMT Kirby Drive437 Urban principal arterials Harris County247 State of Texas233

 Focus on areas of interest  Determine areas of high incidence  Assist with comprehensive review  CrimeStat® Spatial Statistics Program Hot Spot Analyses

Issues for Consideration  Process is time consuming  Full-time process – staff requirements  Quality control is CRITICAL!  Need a good machine

Questions?