Improving safety for slow-moving vehicles on Iowa's high speed rural roadways

Kinzenbaw, Caroline
Major Professor
Shauna Hallmark
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Civil, Construction, and Environmental Engineering

Slow-moving vehicles are commonly found on the rural roads of Iowa. Common slow-moving vehicles in Iowa were analyzed as a part of this thesis which includes farm, construction, maintenance, and all-terrain vehicles as well as mopeds. Though slow-moving vehicle crashes represent a very small percentage of crashes in Iowa, the high speed differential of these vehicles and other traffic can result in higher severity crashes. It is important to determine the crash characteristics that tend to result in higher severity crashes and develop safety standards to help reduce those high severity crashes. This thesis analyzes the commonalities of laws across the nation pertaining to slow-moving vehicle safety. It also contains a 3-year analysis of crashes in Iowa involving slow-moving vehicles and a statistical modeling of farm vehicle crash severity to determine crash characteristics that make a crash more likely to result in a high or low crash severity. The SMV Emblem is the most common safety requirement from state to state, though many differences are observed across the nation amongst other safety features. The circumstances found to increase crash severity in the rural farm vehicle crash model were when the farm vehicle was over 29 years old, when dark conditions existed during the crash, and when the crash occurred during the months of June, July, and August. The animal pulling the buggy was a common cause of collision of the crashes involving horse-drawn buggies. The moped/all-terrain vehicle group had the highest fatality rate of all four groups analyzed. About 70% of the rural multiple vehicle crashes involving moped/all-terrain vehicles resulted from an incorrect action by the moped/all-terrain vehicles. Also, 60% of the crashes involved moped/all-terrain vehicles were driven by a driver under the age of 24. Construction and maintenance vehicles were found to be responsible for fewer than 35% of the rural crashes in which they were involved. From these analyses, recommendations were made with the purpose of reducing the severity of crashes involving slow-moving vehicles in Iowa.