文档介绍：Pawlovich, Li, Carriquiry, Souleyrette, Stout, and Welch 1
3rd Urban Street Symposium
June 24-27, 2007 Seattle, Washington
IOWA’S EXPERIENCE WITH 4-LANE TO 3-LANE CONVERSIONS
AUTHORS:
Michael D. Pawlovich, ., . Wen Li, .
Iowa Department of Transportation, Iowa State University,
Office of Traffic and Safety (TAS) Department of Statistics
800 Lincoln Way 102 Snedecor Hall
Ames, Iowa 50010 Ames, Iowa 50011
Michael.******@ ******@
Alicia Carriquiry, . Reg Souleyrette, ., .
Iowa State University, Iowa State University, Civil Engr./Center for
Department of Statistics Transportation Research and Education (CTRE)
102 Snedecor Hall 2711 South Loop Drive, Suite 4700
Ames, Iowa 50011 Ames, Iowa 50010
******@ ******@
Tom Stout, ., . Tom Welch, .
Iowa State University, Civil Engr./CTRE Iowa Department of Transportation/TAS
2711 South Loop Drive, Suite 4700 800 Lincoln Way
Ames, Iowa 50010 Ames, Iowa 50010
******@ Tom.******@
ABSTRACT
Over the past couple decades, Iowa has converted several 4-lane urban roadways to 3-lane
sections. Most of these have been on low volume roads in munities. Recently,
multiple analyses, both standard before-after and Bayesian, have been conducted to explore the
safety and operational impacts of these conversions or road diets. Each of these analyses have
shown positive impacts of the 4-lane to 3-lane conversions in Iowa. As a couple of years have
passed since the initial analyses and as the Bayesian analysis had not considered severity
concerns, the analysis was updated with these additional years to extend the after periods for the
sites and to include a severity analysis. Within this paper, the results of these latter analyses are
explored, with emphases on the data, results, and possible future applications of these
conversions. Relative to total cr