GIS Display and Analysis of Crash GIS Display and Analysis of Crash DataData

Gautam Mistry

University of Alabama, Tuscaloosa

Prepared for:

29th International Traffic Records Forum

July 15, 2003

ObjectivesObjectives

– Mapping crashes stored in Critical Analysis

Reporting Environment (CARE) on maps using

GIS

– Spatial Analysis of mapped crashes to identify

patterns and hotspots

CARECARE

Critical Analysis Reporting Environment

– Database maintained by the state of Alabama

– Detailed information about vehicular crashes

– Information can be retrieved by “data mining”

– Crashes presented in tabular form and graphically

in a linear form

CARECARE

Crashes can be selected meeting specific criteria

Crash locations verbally described without coordinates

State routes are graphically represented by a line and

number of crashes represented as stack of points at

mileposts shown as numbers

Graphical display does not correlate with roadway

features such as curves, bridges, rail-road crossings,

and etc.

CARE Location DataCARE Location Data CARE stores crash locations in the form of nodes CARE stores crash locations in the form of nodes

(intersection), links (roads), and route milepost (intersection), links (roads), and route milepost (highways)(highways)– Crashes at intersections are identified by node Crashes at intersections are identified by node

numbersnumbers

– Crashes on roads are identified by three fields: Link_ID, Crashes on roads are identified by three fields: Link_ID,

Node_1, Node_2Node_1, Node_2

– Crashes on highways are identified by the route and Crashes on highways are identified by the route and

milepost at which the crash occurredmilepost at which the crash occurred

Creating Common FieldsCreating Common Fields To connect the CARE data to the GIS roads layer, a To connect the CARE data to the GIS roads layer, a

common field is required to be created for nodes and linkscommon field is required to be created for nodes and links

– Value of Node_1 is inserted in the column Connect_ID to represent Value of Node_1 is inserted in the column Connect_ID to represent

crashes on intersectionscrashes on intersections

– The three fields describing links are concatenated to a single entity The three fields describing links are concatenated to a single entity

and placed under a separate column Connect_ID to represent and placed under a separate column Connect_ID to represent

crashes on linkscrashes on links

– A table containing crashes were directly added to the GIS file as A table containing crashes were directly added to the GIS file as

an event table to represent the crashes in mile-posted highwaysan event table to represent the crashes in mile-posted highways

GIS MapGIS Map

Nodes layer was created, and node numbers

were assigned for each intersection

Link number (Link_ID) and node numbers

(Node_1, Node_2) were manually inserted in the

Roads layer for each road segment

Routes were created for highways and milepost

were assigned to the ends of the routes

CARE Linked to GISCARE Linked to GIS

Node_ID column from nodes layer was related

to Connect_ID column from CARE

Connect_ID column in CARE database was

related to Connect_ID column from roads layer

in GIS for crashes that occurred on links

Highway crashes are mapped on the routes

created in GIS by dynamic segmentation

®

Tuscaloosa CountyBASE MAP

Spatial AnalysisSpatial Analysis

Hotspots are identified to indicate the Hotspots are identified to indicate the locations with high crash frequencies locations with high crash frequencies using thematic mapping and bufferingusing thematic mapping and buffering

Legend

Number of Crashes on Links

0

1

2

3

®

Thematic Map for Links

$+")

®

Legend

Crashes at Nodes

1 - 5

6 - 10

") 11 - 15

$+16 - 20

Thematic Map for Nodes

®Legend

0.5-mile Buffer of Major Highways

roads

Number of Crashes

0

1

2

3

Crashes on Links within 0.5-mile Buffer from

Major Highways

Spatial AnalysisSpatial Analysis

Crashes mapped on GIS can be spatially correlated to roadway features such as bridges, railroad crossings, crossroads, and etc.

!(

!(

!(

!(

#*$+ !(

®Legend

roads

rail

Crashes at Railroad Crossings

!( 1

#* 2

") 3

$+ 7

Thematic Map of Crashes at Rail-road Crossings

®Legend

roads

rail

Number of Crashes on Links

0

1

4

Crashes on Links near Rail-road Crossings

Spatial AnalysisSpatial Analysis

Crashes on Interstate and State Crashes on Interstate and State Highways were mapped according to Highways were mapped according to the milepost at which the crashes the milepost at which the crashes occurred using dynamic segmentationoccurred using dynamic segmentation

!(

!(

!(

!(!(

!(

!(!(!(!(!(

!( !( !(!(

!( !( !( !(!( !( !( !(!(

!(!(

!(!(!(

Legend

!( Crash Locations

I - 20/59

county

®

!(

!(!(

!(!(!(!(!(!(!(!(

!( !(!(!(!( !(!( !( !(!( !(!(!(

!( !(!(!(!(

Tuscaloosa County

Crashes on I-20/59 According to Milepost

ConclusionsConclusions This GIS application allows user to view the crashes on This GIS application allows user to view the crashes on

road map, which gives spatial representation of crashesroad map, which gives spatial representation of crashes

It enables CARE data to be correlated with existing It enables CARE data to be correlated with existing

roadway features like bridges, rail-road crossings, and roadway features like bridges, rail-road crossings, and

etc.etc.

It enables identification of hotspots and crash patterns It enables identification of hotspots and crash patterns

at nodes, links, or route milepostsat nodes, links, or route mileposts

Use of multi-year data helps in graphical representation Use of multi-year data helps in graphical representation

of before and after analysisof before and after analysis

QuestionsQuestions