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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
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
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
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
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