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FHWA-RD-99-128
FOREWORD
This report provides direct input into the Accident Analysis Module (AAM) of
the Interactive Highway Safety Design Model. The AAM is a tool that highway
engineers can use to evaluate the impacts of highway design elements in project
planning and preliminary design. Three crash models were developed relating
crashes to three types of rural intersections. These types are: (1) three-legged
intersections with major four-lane roads and minor two-lane roads that are stop-controlled,
(2) four-legged intersections with major four-lane roads and minor two-lane
roads that are stop-controlled, and (3) signalized intersections with both major
and minor two-lane roads.
Elaborate sets of data were acquired from State data sources (Michigan and
California) and collected in the field. The final data sets consist of 84 sites
of three-legged intersections, 72 sites of the four-legged intersections, and
49 sites of the signalized intersections. Negative binomial models -- variants
of Poisson models that allow for overdispersion -- were developed for each of
the three data sets. Significant variables included major and minor road traffic;
peak major and minor left-turn percentage; peak truck percentage; number of
driveways; and channelization, intersection median widths, vertical alignment,
and, in the case of signalized intersections, the presence or absence of protected
left-turn phases. Separate models were developed for crashes resulting in injuries
and total crashes.
Michael F. Trentacoste
Director, Office of Safety
Research and Development
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1. Report No.
FHWA-RD-99-128
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2.
Government Accession No. |
3.
Recipient's Catalog No. |
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4. Title and Subtitle
Crash Models for Rural Intersections: Four-Lane by Two-lane Stop-Controlled
and Two-lane by Two-lane Signalized
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5. Report Date
October 1999
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6. Performing Organization
Code
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7. Author(s)
Andrew Vogt
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8. Performing Organization
No.
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9. Performing Organization
Name and Address
Pragmatics, Inc.
7926 Jones Branch Drive, Suite 711
McLean, Virginia 22102
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10. Work Unit No.
(TRAIS)
3A5A
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11. Contract or Grant
No.
DTFH61-96-C-00076
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12. Sponsoring Agency
Name and Address
Office of Safety R&D
Federal Highway Administration
6300 Georgetown Pike, T-304
McLean, Virginia 22101-2296
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13. Type of Report
and Period Covered
Final Report
September 1996 - May 1999
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14. Sponsoring Agency
Code
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15. Supplementary
Notes
Contracting Officer's Technical Representative (COTR) - Joe G. Bared,
HRDS
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16. Abstract
This report describes the collection, analysis, and modeling of crash
and roadway data for intersections on rural roads in California and
Michigan for the years 1993-1995. Three classes of intersection are
considered: (1) three-legged intersections with major four-lane roads
and minor two-lane roads that are stop-controlled, (2) four-legged intersections
with major four-lane roads and minor two-lane roads that are stop-controlled,
and (3) signalized intersections with both major and minor two-lane
roads. Data was acquired from the Highway Safety Information System,
State and Federal photologs, and field work at all intersections. The
field work included morning and evening traffic counts by movement and
vehicle type as well as alignment measurements out to 800 feet (244
meters) along the major road. The final data sets consist of 84 three-legged
intersections, 72 four-legged intersections, and 49 signalized intersections.
Other variables collected include Roadside Hazard Rating, number of
driveways, channelization, intersection angles, and speed limits.
Negative binomial models -- variants of Poisson models that allow for
overdispersion -- were developed for each of the three data sets. Significant
variables included major and minor road traffic, peak major and minor
left-turn percentage, number of driveways, channelization, median widths,
vertical alignment, and, in the case of signalized intersections, the
presence or absence of protected left-turn phases and peak truck percentage.
Models are developed for all crashes within 250 feet (76 meters) of
the intersection center, for intersection-related crashes within 250
feet (76 meters), and for injury crashes. For injury crashes, intersection
angle and minor road posted speed are significant. Models of crashes
at signalized intersections by approach flows are also investigated,
and other model forms are proposed for future consideration.
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17. Key Words
Highway safety, crash prediction models, negative binomial regression,
intersection design
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18. Distribution
Statement
No restrictions. This document is available to the public through the
National Technical Information Service, Springfield, VA 22161.
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19. Security Classification
(of this report)
Unclassified
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20.
Security Classification (of this page)
Unclassified
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21. No. of Pages
182
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22.
Price |
Form DOT F 1700.7 Reproduction
of completed page authorized
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