Iowa Department of Transportation
Iowa Highway Research Board
Halil Ceylanhceylan@iastate.edu email >
Sunghwan Kimsunghwan@iastate.edu email >
Associate Director, PROSPER
In-Ho Choicho@iastate.edu email >
About the research
Iowa state law limits weight of vehicles by axle and gross (total) weight. While these laws standardize traditional vehicles by size and weight, the agricultural implement industry is a vehicle sector that has changed substantially in recent years, most notably in terms of manufacturing larger vehicles. This has resulted in heavier farm implements that, if filled to capacity, are substantially overweight in terms of current law. Similarly, there are other superloads and heavy traffic generators (non-divisible vehicles, trucks carrying wind turbines, transport from-to concentrated animal feeding operations, and other industries) that can potentially become overweight. Local law enforcement typically does not have the equipment necessary to measure overweight vehicles, so most counties report overloaded vehicles to their Department of Transportation (DOT) Motor Vehicle Enforcement Agency. However, response from DOT Vehicle Enforcement is not always timely, and many reports receive no response at all. Given this legal and enforcement environment, when designing and constructing county roads, counties must adapt by accounting for the percentage of traffic overweight vehicles traveling on the county road system. Currently, since this percentage (i.e., % superloads) is more or less subjective based on guesswork, there is a need for a better way of determining more accurate traffic types and counts that take into account the presence of superloads.