Effectiveness of Paved Shoulders in Iowa

Principal Investigator:

Shauna Hallmark, shallmar@iastate.edu (other projects)

Co-Principal Investigator:

• Tom McDonald, tmcdonal@iastate.edu (other projects)

Project Status: In Progress

Start Date: 12/01/2005
End Date: 11/30/2007


Research Objective: The value of paved shoulders has been acknowledged for many years by transportation agencies and road users alike. Improved safety and convenience as well as reduced routine maintenance costs are all common benefits attributed to paved shoulders. In 2004, Iowa adopted a paved shoulder policy for higher volume roads, but a broad diversity of paved shoulder types has been utilized for many years in the state.

Although several types and designs of paved shoulders have been constructed by contract and installed by agency maintenance staff for many years, an extensive analytical analysis of safety benefits has not been undertaken. Many design and maintenance decisions regarding paved shoulders must rely on subjective data and intuitive judgment. As a result there is a need to quantify the safety impacts of paved shoulders so that agencies can make better decisions on the costs and benefits of improvements.

In order to address this need, this research intends to evaluate the effectiveness of paved shoulders in reducing the number and/or severity of crashes. The main objectives of this research effort will be to

--Assess safety impacts of the Iowa DOT paved shoulder policy since implementation in 2004, both analytically and subjectively.

--Evaluate the potential safety benefits of paved shoulders across a wide spectrum of applications including; design criteria, traffic volumes and mix, terrain, and road type and classification.

This study will concentrate on 2-lane rural, higher speed (45 mph) roads. The Iowa DOT's extensive history of paved shoulder placement will permit safety and physical performance analysis over a wide range of traffic volumes and types, roadway classifications and terrain, and design characteristics. In addition, opinions of maintenance staff and various types of road users will be sought.

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