Zachary Hans

A mixed logit analysis of two-vehicle crash severities involving a motorcycle

Using motorcycle crash data for Iowa from 2001 to 2008, this paper estimates a mixed logit model to investigate the factors that affect crash severity outcomes in a collision between a motorcycle and another vehicle. These include crash-specific factors (such as manner of collision, motorcycle rider and non-motorcycle driver and vehicle actions), roadway and environmental conditions, location and time, motorcycle rider and non-motorcycle driver and vehicle attributes. The methodological approach allows the parameters to vary across observations as opposed to a single parameter representing all observations. Our results showed non-uniform effects of rear-end collisions on minor injury crashes, as well as of the roadway speed limit greater or equal to 55mph, the type of area (urban), the riding season (summer) and motorcyclists gender on low severity crashes. We also found significant effects of the roadway surface condition, clear vision (not obscured by moving vehicles, trees, buildings, or other), light conditions, speed limit, and helmet use on severe injury outcomes.

Deer-vehicle collisions, deer density, and land use in Iowa's urban deer herd management zones

Many states are striving to keep their deer population to a sustainable and controllable level, while maximizing public safety. In Iowa, measures to control the deer population include annual deer hunts and special deer herd management plans in urban areas. While these plans may in effect reduce the deer population, traffic safety in these areas has not been fully assessed. Using deer population data from the Iowa Department of Natural Resources and data on deer-vehicle crashes and deer carcass removals from the Iowa Department of Transportation, we examine the relationship between deer-vehicle collisions, deer density, and land use in select urban deer management zones in Iowa. Further, we estimate models to investigate the factors that influence the frequency and severity of deer-vehicle crashes in these zones. The estimation results showed that multiple factors affect deer-vehicle crashes and corresponding injury outcomes in urban management zones. The identified roadway and non-roadway factors could be useful for identifying locations on the transportation system that significantly impact deer species and safety, and determining appropriate countermeasures for mitigation.

Identifying and Measuring Horizontal Curves and Related Effects on Highway Safety

Although crash rates on U.S. highways have decreased in recent years, nearly 34,000 fatalities were reported for 2009. Many of these deaths occur on high-speed rural roads, where crashes at curves are particularly likely. To analyze and systematically mitigate risk on highway curves, the curves must first be located and measured. This article presents a hybrid manual-computer method that uses a geographic information system (GIS)-based procedure, global positioning system (GPS) road data, circular regression, chord equations, and line simplification to identify and measure curves. Measures are validated with “as-built” design plans, and predicted safety-performance sensitivity to measurement errors is tested using Highway Safety Manual functions. Results indicate predicted performance is more sensitive to curve parameter errors for short tight curves and to errors in length than to errors in radius. The length measurement–induced errors may be reduced by analyzing tangents and curves as a whole. The impact of radius-measurement error is shown to be dependent on curve length. Although the ability of the method to measure curve parameters over a wide range of length and radius is limited, the curve identification strategy provides an efficient means to identify curves for implementation of low-cost safety improvement measures.

Validation of U.S. Road Assessment Program Star Rating Protocol: Application to Safety Management of U.S. Roads

The U.S. Road Assessment Program, in cooperation with road assessment programs in other countries, has developed a protocol to assign ratings to roads on the basis of the presence or absence of key design features related to safety. This protocol rates roads by assigning them one to five stars according to approximately 20 key roadway safety features. A recently developed web-based software tool uses the roadway inventory data on which the star ratings are based to identify cost-effective safety improvement programs for the road networks covered by the ratings. The research results are presented to validate the relationship between the star ratings and crash rates for selected roadways. The research developed star ratings for approximately 3,000 mi of rural and urban roadways of various types in Iowa and Washington State and compared the star ratings with crash rates for the same roads. Relationships between star ratings and crash rates were found for two-lane undivided highways, four-lane undivided highways, and four-lane divided nonfreeways. No clear relationships could be demonstrated for freeways because the design characteristics of freeways are very uniform.

Bridge Rail and Approach Railing for Low-Volume Roads in Iowa

Bridge rail and approach guardrails provide safety to drivers by shielding more-hazardous objects and redirecting vehicles to the roadway. However, guardrails increase both the initial and maintenance costs of a bridge while adding another object that vehicles may strike. According to current reports, most existing bridges for low-volume roads (LVRs) in the state of Iowa do not have bridge rails that meet current standards. The primary objective of this research was to provide information about bridge rail and approach guardrail on LVRs in Iowa. In support of this objective, statewide descriptive, statistical, and economic crash analyses were performed. The statewide crash analysis found that the overall number of crashes at or on the more than 17,000 inventoried and other noninventoried LVR bridges in Iowa during an 8-year period was fewer than 350, a number that represents less than 0.1% of the statewide reportable crashes. Statistical analysis showed that the frequency of vehicle crashes was higher on bridges with a smaller width in relation to the roadway width. The frequency of crashes appeared to be overrepresented at night or in dark conditions. Systemwide, benefit–cost analyses yielded extremely low benefit–cost ratios for statewide bridge rail improvements. However, specific sites where safety concerns exist should be addressed. Overall, each bridge and its crash history should be evaluated independently to determine beneficial safety impacts.

Integrated Approach to Pavement Marking Management

Providing good pavement marking performance is an essential component of the transportation system. According to Tom Welch, state safety engineer for the Iowa Department of Transportation (DOT), “Every older driver forum has included a consistent demand for brighter and more durable pavement markings.” This paper summarizes some management tools developed for Iowa DOT as part of a pavement marking management system (PMMS). A summary of how retroreflectivity data are used statewide in managing pavement marking performance is provided as well as a discussion of how the PMMS was integrated with other infrastructure management resources for Iowa DOT.

Most Likely Bridges as Roosting Habitat for Bats: Study for Iowa:

Bats play an important role in the natural balance of many ecosystems. There has been a growing concern about the bat population in the United States, mainly because of white-nose syndrome (WNS). The primary objective of this work was to better understand what types of bridges are the most likely to be used by bats as roosting locations. In one of the most comprehensive studies in the United States to date, 517 structures in the state of Iowa were inspected for evidence of bat roosting. Logistic regression models were fitted to identify structure, land cover distribution, and predicted bat species distribution characteristics that increase the probability of bat roosting. The final model indicated that probability of bat roosting on bridges increases under the following conditions: structures are prestressed concrete continuous, prestressed concrete or steel continuous; increased superstructure height above ground; increased superstructure depth; increased wetland coverage within a 0.1-mile radius of the structure; and increased number of potential bat species present at the location. The findings show that bridge characteristics, combined with land cover and bat species distribution data, are significant for higher probabilities of bat roosting. This information can be useful to transportation agencies as they plan bridge maintenance and renewal and can also help conservation efforts targeted toward bats. It is thought that the integration of objective, geospatial land cover data with potential bat presence data, and estimation of quantitative and relative influence of variables on probability of bat roosting are unique to this study.