CTRE is an Iowa State University center, administered by the Institute for Transportation.

Address: 2711 S. Loop Drive, Suite 4700, Ames, IA 50010-8664

Phone: 515-294-8103
FAX: 515-294-0467

Website: www.ctre.iastate.edu/

Iowa State University--Becoming the Best

Four-Lane to Three-Lane Analysis


Principal investigator: Reginald Souleyrette

Other authors: Thomas Stout

Student researcher: Thomas B. Stout

Project status


Start date: 01/01/05
End date: 06/30/05


Project web page: http://www.ctre.iastate.edu/research/4laneto3lane.htm

Related publications:

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Sponsor(s):Iowa Department of Transportation

About the research

Abstract: The safety impacts of the conversion of a 4-lane undivided roadway to a 3-lane roadway are evaluated using classical before and after studies, with yoked pairs and the cities of some 14 sites. Iowa DOT databases were used to evaluate the changes in the frequency of crashes, rate of crashes, types of injuries, major causes of crashes, key age groups, single vehicle run-off-road crashes, and direction of travel coupled with initial action. The results indicated that the frequency of crashes was reduced by about 26%, when other changes were accounted for, that serious injuries were reduced, and that older drivers had a reduced risk of crashing