Improving Safety for Slow Moving Vehicles on Iowa’s High-Speed Rural Roadways: Final Report

Hawkins, Neal; Kinzenbau, Cari; Hallmark, Shauna · 2009 · ROSA P / Iowa State University. Institute for Transportation

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Summary

This report addresses the safety challenges posed by slow-moving vehicles (SMVs)—defined as vehicles unable to maintain 25 mph, including farm equipment, construction vehicles, and horse-drawn buggies—on Iowa’s high-speed rural roadways. The research was motivated by the disproportionate severity of SMV crashes; although infrequent, crashes involving agricultural vehicles are approximately five times more likely to result in fatalities than other crash types. The study aims to identify specific safety issues and develop targeted countermeasures through a combination of statistical analysis and community engagement. The methodology comprised three primary components: a literature review of national SMV statistics and laws, a quantitative analysis of Iowa crash data from 2004 to 2006, and qualitative feedback from SMV operators. The crash study analyzed 1,203 rural SMV incidents, while the qualitative phase involved public meetings and field reviews with Amish communities in Buchanan and Davis Counties, as well as interviews with farmers in Marion County. This mixed-methods approach allowed the researchers to correlate statistical trends with the practical concerns of the operators. The findings revealed that farm vehicles accounted for 50% of SMV crashes, followed by construction/maintenance vehicles (19%) and horse-drawn vehicles (1%). Crash patterns varied by vehicle type, with significant risks associated with speed differentials, inadequate shoulder width, and motorist frustration. Specific concerns highlighted by the horse-and-buggy community included dangerous shoulder maintenance practices (such as large asphalt chunks), insufficient separation from large trucks, and the hazard posed by rumble strips to horses and buggy wheels. Farmers reported that pulling over was often unsafe due to soft or obstructed shoulders, and that passing motorists frequently failed to provide adequate clearance. Additionally, farmers noted that flashing yellow lights elicited better reactions from motorists than the standard SMV emblem. The report concludes that improving SMV safety requires a systematic, collaborative approach involving state, county, and city agencies alongside SMV communities. Recommendations include identifying specific problem routes, reviewing roadway infrastructure (such as signage, shoulder width, and pavement treatments), and coordinating consistent safety campaigns. The authors emphasize that solutions must be tailored to the distinct needs of different SMV types, such as distinguishing between motorized farm equipment and horse-drawn vehicles. SMV operators are advised to exceed minimal lighting requirements and communicate safety concerns to agencies, while agencies are urged to engage in dialogue with local groups to implement long-term, context-specific safety improvements.

Key finding

Crashes involving slow moving agricultural vehicles are approximately five times more likely to result in a fatality than other crash types, with farm equipment involved in 50% of the 1,203 recorded incidents between 2004 and 2006.

Methodology

dataset

Sample size: 1203

Provenance

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Summary generated by qwen3.6-27b-prismaquant on 2026-06-10; verification: verified.

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