Studies have shown that roadway use of ORVs is clearly a dangerous practice [7, 12–15, 19], but the impact of legislation allowing ORV use on public roads has not previously been quantified. Our study shows that legislation allowing the use of ORVs on public roadways was associated with significantly increased roadway and total crashes. Overall, we found a 58% increase in crashes in counties after permissive ORV roadway ordinance implementation as compared to before passage and as compared to counties that did not pass such ordinances. Based on this and extrapolating from the most recent 5 years of CPSC injury and death data from Iowa [1, 2], a 58% increase in ORV crashes could result in an estimated 776 additional emergency department visits and 5 additional deaths per year in the state of Iowa.
ORVs are designed for off-road use only [3–5, 7]. They have a relatively narrow track so they can travel between obstacles and a high clearance that allows them to drive over rough terrain. However, this gives ORVs a relatively high center of gravity that increases their risk of rollover. In addition, roadway vehicle tires have shallow tread designed to continually grip and release roadway surfaces. In contrast, ORVs have low-pressure tires with knobby tread that are designed to grab off-road terrain but can unevenly and unpredictably grab public roadway surfaces leading to loss of ORV control [4–7, 24, 25]. Roadway vehicles also have an open rear differential that allows the outer tires to travel faster than the inner tires, creating a tighter turning radius. ATVs and many UTVs have a solid rear axle or locked rear differential, and operators can easily misjudge the speed they need to slow down to in order to successfully negotiate a turn or curve [4–7, 24, 25]. Thus, ORVs have a number of off-road design features that increase the risk of loss of control and rollover, especially at the speeds often traveled on public roads.
In our study, many roadway ORV crashes were noted both in counties before permissive ordinance passage and in counties where usage remained illegal, suggesting inadequate enforcement of ORV roadway prohibition. Previous studies found limited and variable enforcement of restrictive ORV laws, thus limiting their potential to prevent deaths and injuries [26]. If this legislation were better enforced, the potential impact of prohibitive ORV roadway legislation may be considerably greater than that seen in our study. Strategies are needed to support enforcement of restricted ORV roadway access and should be targeted toward jurisdictions that have these laws in place.
In the course of cataloguing ORV ordinance data for all 99 Iowa counties, the rationales for permissive roadway ordinances by supporters were occasionally noted in board of supervisor meeting transcripts. In some cases, county officials and members of the public cited a desire to travel between different farmland plots via connecting public roads for work. However, a longstanding state law already allowed the use of ORVs on public roadways for agricultural purposes. Despite the lack of data demonstrating economic benefit to opening up public roads to ORV use, individuals in some counties expressed concerns of potentially losing business to a neighboring county that had already passed an ordinance. This phenomenon was a likely contributor to the geographic spread of ordinances from a nidus county to adjacent counties throughout the study period.
As this study was being conducted in 2021–2022, the Iowa state legislature began circulating a bill to both legalize the use of ATVs/UTVs on county public roads statewide and to restrict the ability of county boards of supervisors to limit such usage [27]. Despite opposition by health experts, law enforcement organizations and even some off-highway vehicle associations [28], the legislature passed House File 2130. In June of 2022, the bill was signed into law by the governor, thereby enacting the legislation investigated in this study across the entire state [27].
Limitations
Permissive OHV roadway laws, similar to that studied, have been enacted in other states or counties of other states. However, this study was performed in the state of Iowa and may not be generalizable to other states and counties. The sources for our crash database are robust but not all-inclusive, as crashes may have been unreported, may have lacked detailed vehicle categorization by state or healthcare officials resulting in omission from the crash database, and/or may have been excluded from this study due to lack of county-level location information.
As this was a quasi-experimental study, we were evaluating the impact of an exogenous event, i.e., the passing of ordinances, on county-level crash rates. Other factors may also have affected crash rates across time and location, though ordinance enactment remains the most plausible cause. One way we investigated the effect of location was to analyze the change in crash rate only in the subset of counties that passed an ordinance (excluding the crashes from counties that did not). These counties are generally more rural, with lower population density than counties that never passed ordinances. However, we found no skew of the results when limiting to these counties, with an almost identical 59% increase in crash rates on all surfaces and an even higher 64% increase in crash rate when looking at on-road only crashes in this subset of counties.