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Iowa State University--Becoming the Best

Paved Shoulders on Primary Highways in Iowa: An Analysis of Shoulder Surfacing Criteria, Costs, and Benefits


Principal investigators:

Co-principal investigators:

Project status


Start date: 07/01/00
End date: 06/30/01




Sponsor(s): Iowa Department of Transportation

About the research

Abstract: The value of providing paved shoulders adjacent to many higher volume roadways has been accepted in many states across the country. Iowa?s paved shoulder policy is considerably more conservative than neighboring states, particularly on rural four-lane and high-volume two-lane highways.

The objectives of this research were to examine current design criteria for shoulders employed in Iowa and surrounding states, compare benefits and costs of alternative surface types and widths, and make recommendations based on this analysis for consideration in future design policies for primary highway in Iowa.

The report finds that many safety and maintenance benefits would result from enhancing Iowa?s paved shoulder and rumble strip design practices for freeways, expressways, and Super 2 highway corridors. The benefits of paved shoulders include reduced numbers of certain crashes, higher capacity potentials, reduced maintenance, enhanced opportunities for other users such as bicyclists, and even possible increased longevity of pavements. Alternative paved shoulder policies and programming strategies are also offered, with detailed assessments of the benefits, costs, and budget impacts.