Analysis of Impact of Road Signs on Traffic Accidents in Fairfax County, Virginia

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Analysis of Impact of Road Signs on Traffic
Accidents in Fairfax County, Virginia

• Presentation by
• Karen Harner
• Tracy Holloman
• Katie Stanley
• April 17, 2003

2
Outline

• Goal of project
• Gathering data sources
• Methodology
• Sample Query
• Uses
• Conclusions

3
Goal of Project

• To determine if there exists a correlation
  between certain road signs and incidences of
  traffic accidents at various intersections on
  Route 236 in Northern Virginia

4
Gathering Data Sources

• VDOT Road Layer from the geostat lab
• VDOT Fairfax signs layer
• VDOT Highway and Traffic Records Information
  System (HTRIS) Crash Data

5
Methodology

• Step1 Gather data sources
• Step 2 Decide on the types of signs to examine
• Step 3 Extract signs to create new layer
• Step 4 Find intersections to investigate
• Step 5 Obtain crash data for intersections
• Step 6 Put information into excel

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Methodology Continued

• Step 7 Digitize points at the intersections
• Step 8 Convert excel files into .dbf format
• Step 9 Add layers to ArcMap
• Step 10 Relate tables to digitized layer
• Step 11 Perform queries to aid in investigation

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MUTCD Codes
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Signs Used

• Sign Message
• Advance Guide Sign
• Center Lane Only
• Direction(al) Arrow
• Guide Sign
• Left Lane Must Turn Left
• Left Turn Only, Signal or Warning

• Sign Type
• R3-5
• R3-6
• R3-7L
• R3-7R
• R3-8
• R3-9A
• R3-9B

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Signs Examined

• 2 different GIS data frames implemented
• 1 based on sign type field (MUTCD codes)
• 1223 signs
• 2 based on sign message field
• 4533 signs

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Explanation of Crash Data

• Table 1 1 row per intersection (Total Accident
  Quantities)
• Table 2 Breakdown of accidents by intersection
  (when available)

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Adding Layers to ArcMap

• Add roads layer, digitized crash sites and signs
• Add two tables
• Join Digitized Layer and Table 1
• Relate Digitized Layer and Table 2
• Relate Table 2 to Digitized Layer

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Study Area
Crash Sites w/in .2 mi. of sign layer
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Identify Button
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Attribute Tables
Crash Sites
Table 1
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Related Table
Related Table Crash Data 2
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Info on Individual Accidents
Related Table w/ info on individual intersections
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Statistics for Message Signs
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Statistics for MUTCD Code Signs
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Uses for this GIS

• Can select intersections by their distance from
  guide signs
• Use identify button to determine total crashes
• Table 2 individual crash breakdown
• Determine relationship between weather conditions
  and accident types

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Conclusions

• Improvement areas
• Add volume counts
• Greater number of intersections
• Narrow sign scope
• Try to determine extent of correlation between
  sign names and the MUTCD codes
• Signalized or Non-signalized intersection

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Questions ??