Konstantina Gkritza

Mixed logit analysis of safety-belt use in single- and multi-occupant vehicles

In this paper we demonstrate a modeling approach that can be used to better understand the use of safety belts in single- and multi-occupant vehicles, and the effect that vehicle, roadway and occupant characteristics have on usage rates. Using data from a roadside observational survey of safety-belt use in Indiana, a mixed (random parameters) logit model is estimated. Potentially interrelated choices of safety-belt use by drivers and front-seat passengers are examined. The approach we use also allows for the possibility that estimated model parameters can vary randomly across vehicle occupants to account for unobserved effects potentially relating to roadway characteristics, vehicle attributes, and driver behavior. Estimation findings indicate that the choices of safety-belt use involve a complex interaction of factors and that the effect of these factors can vary significantly across the population. Our results show that the mixed logit model can provide a much fuller understanding of the interaction of the numerous variables which correlate with safety-belt use than traditional discrete-outcome modeling approaches.

Cost Savings Analysis of Performance-Based Contracts for Highway Maintenance Operations

Highway agencies around the world are undergoing major changes in their traditional maintenance practices, including the privatization of entire sections of highway routine maintenance activities. Performance-based contracts (PBC) are an option in such privatizing efforts. This paper presents a methodology to estimate the likelihood and amount of cost savings associated with the application of PBC for highway maintenance operations. Using data on maintenance contracts from around the world, we develop models that can be used to compare several contracting methods and include variables such as contract duration, activity type, and contract size. We find that large projects with strong competition, long duration and extension periods, long outsourced road sections that incorporate crack sealing, pothole repair, illumination repair/maintenance, and mowing activities, favor outsourcing under PBC. Our methodology can be useful to transportation agencies for making decisions about the use of PBC and other methods of maintenance outsourcing at the preplanning phase.

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.

Modeling motorcycle helmet use in Iowa: Evidence from six roadside observational surveys

This paper investigates the influence of type of roadway, weather conditions and other factors on motorcycle helmet use rates in Iowa. Using data from six statewide roadside observational surveys of motorcycle helmet use, a bivariate probit model is estimated. The applied methodological approach allows for potentially interrelated choices of motorcycle helmet use by drivers and passengers to be examined. The estimation results can enhance our understanding of other factors than state helmet laws which correlate with motorcycle rider helmet use, and the effect that the presence of a passenger has on motorcycle driver helmet use rates.

An empirical analysis of farm vehicle crash injury severities on Iowa's public road system

Farm vehicle crashes are a major safety concern for farmers as well as all other users of the public road system in agricultural states. Using data on farm vehicle crashes that occurred on Iowas public roads between 2004 and 2006, we estimate a multinomial logit model to identify crash-, farm vehicle-, and driver-specific factors that determine farm vehicle crash injury severity outcomes. Estimation findings indicate that there are crash patterns (rear-end manner of collision; single-vehicle crash; farm vehicle crossed the centerline or median) and conditions (obstructed vision and crash in rural area; dry road, dark lighting, speed limit 55 mph or higher, and harvesting season), as well as farm vehicle and driver-contributing characteristics (old farm vehicle, young farm vehicle driver), where targeted intervention can help reduce the severity of crash outcomes. Determining these contributing factors and their effect is the first step to identifying countermeasures and safety strategies in a bid to improve transportation safety for all users on the public road system in Iowa as well as other agricultural states.

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.

National long-term investment planning for energy and transportation systems

The most significant energy consuming infrastructures and the greatest contributors to greenhouse gases in the US today are electric and freight/passenger transportation systems. Technological alternatives for producing, transporting, and converting energy for electric and transportation systems are numerous. Selecting from among them requires long-term assessment since these capital-intensive infrastructures take years to build with lifetimes approaching a century. The advent of electrified transportation creates interdependencies between the two infrastructures that may be both problematic and beneficial. We are developing modeling capability to perform long-term electric/transportation infrastructure design at a national level, accounting for their interdependencies. The approach combines network flow/DC-flow modeling with a multiobjective solution method. We motivate the need for this work by summarizing attributes and issues related to the investment planning problem so as to find minimum-cost, low-emission, resilient infrastructure portfolios for the future. State-of-the-art energy planning models are summarized, and we describe our software design which includes a multiobjective evolutionary algorithm with a network linear programming cost minimization fitness evaluation, together with metrics for evaluating resiliency and sustainability.

National Energy and Transportation Systems: Interdependencies within a Long Term Planning Model

The most significant energy consuming infrastructures and the greatest contributors to greenhouse gases for any nation today are electric and freight/passenger transportation systems. Technological alternatives for producing, transporting, and converting energy for electric and transportation systems are numerous. Addressing costs, sustainability, and resiliency of electric and transportation needs requires long-term assessment since these capital-intensive infrastructures take years to build with lifetimes approaching a century. Yet, the advent of electrically driven transportation, including cars, trucks, and trains, creates potential interdependencies between the two infrastructures that may be both problematic and beneficial. We are developing modeling capability to perform long-term electric and transportation infrastructure design at a national level, accounting for their interdependencies. The approach combines network flow modeling with a multiobjective solution method. We describe and compare it to the state of the art in energy planning models. An example is presented to illustrate important features of this new approach.

Urban Road Pricing: Modeling Public Acceptance

Acceptability is considered the most important barrier in establishing a congestion pricing scheme. Using data from an extensive questionnaire survey conducted in the central area of Athens, Greece, in 2008, this paper examines attitudes toward traffic congestion, choice of travel mode, and revenue allocation, which can influence the acceptability of congestion pricing. Since one of the major goals of congestion pricing is to discourage personal automobile use, we also examine the choice of mode following the implementation of a congestion pricing system. Further, we developed a multivariate probit model to investigate the factors that influence public perception regarding the effectiveness of six traffic-management measures. Results from this study can assist in better understanding the factors that affect public acceptance of congestion pricing in urban areas.

Interdependencies between Energy and Transportation Systems for National Long Term Planning

The most significant energy consuming infrastructures and the greatest contributors to greenhouse gases for any nation today are electric and freight/passenger transportation systems. Technological alternatives for producing, transporting, and converting energy for electric and transportation systems are numerous. Addressing costs, sustainability, and resiliency of electric and transportation needs requires long-term assessment since these capital-intensive infrastructures take years to build with lifetimes approaching a century. Yet, the advent of electrically driven transportation, including cars, trucks, and trains, creates potential interdependencies between the two infrastructures that may be both problematic and beneficial. We are developing modeling capability to perform long-term electric and transportation infrastructure design at a national level, accounting for their interdependencies. The approach combines network flow modeling with a multiobjective solution method. We describe and compare it to the state-of-the-art in energy planning models. An example is presented to illustrate important features of this new approach.