United States Department Of Transportation Research Articles

Connected Vehicles for Intelligent Transportation Systems [Guest editorial

The papers in this special section focus on the special features and applications supported by connected vehicles (CV) for intelligent transportation systems. CV systems use connectivity (via wireless communications), positioning (via Global Positioning System and digital maps), and data processing to enable vehicles, smart roadway infrastructure, and personal mobile devices to exchange information with each other and to provide road users with both safety and mobility advisories, warnings, and alerts. CV systems are creating new possibilities within the road transportation sector. They promise to reduce greenhouse gas emissions and fuel consumption; improve safety and security; enhance efficiency, mobility, and accessibility; and foster economic opportunities for advanced clean technology jobs and investments. The potential of CVs has been acknowledged with the establishment of ambitious research programs around the globe. In particular, radio spectrum has been allocated in North America, Europe, and Japan for dedicated short-range communications to facilitate safety technologies and applications for Intelligent Transportation Systems. The United States Department of Transportation has been taking steps to mandate car makers to enable vehicle-to-vehicle communication technologies for light vehicles for a safe driving experience. Despite the potential vision of CV systems, there are numerous design challenges remaining to be addressed before their widespread deployment. The aim of this series is to present a collection of high-quality research papers on the state of the art in emerging technologies for CVs, the latest development in standardizations and regulations, as well as the potential services and applications for CV systems.

A screening method for bridge scour estimation and flood adaptation planning utilizing HAZUS-MH 2.1 and HEC-18

The American Society of Civil Engineers’ 2013 Report Card for the Nation’s Infrastructure indicated that over 10 % of the roughly 670,000 bridges in the USA are structurally deficient with a $120 billion investment over the next 15 years required for mitigation. In addition, the Intergovernmental Panel on Climate Change indicates that the frequency of severe precipitation events is increasing as well as associated flooding. These factors coupled with scour as a leading cause of bridge degradation demonstrate a need to develop screening methods for assessing and prioritizing bridges most deserving of adaptation measures. This paper proposes a method for utilizing FEMA’s HAZUS-MH software along with the United States Department of Transportation’s Hydraulic Engineering Circular 18 scour equations to predict the relative scour impact for a bridge to assist in adaptation prioritization. The estimation method develops a scour factor for a bridge using contraction, pier and abutment scour estimates for a base-year and future-year flood event. The scour factor is then used in conjunction with estimated bridge replacement cost to predict monetary damages for a future flood event. The method was validated using repair cost data for eight bridges located in Davidson County (Nashville), Tennessee, from a severe flooding event in May 2010. An extended case study application was also conducted by applying the methodology to a set of flood-prone bridges in the Little Rock, Arkansas area. The results of this research suggest that the proposed methodology may offer municipalities a useful screening tool for prioritizing bridges for adaptation planning.

Progress towards zero, an international comparison: Improvements in traffic fatality from 1990 to 2010 for different age groups in the USA and 15 of its peers

IntroductionIn January 2015, the United States Department of Transportation (USDOT) announced that the official target of the federal government transportation safety policy was zero deaths. Having a better understanding of traffic fatality trends of various age cohorts—and to what extent the US is lagging other countries—is a crucial first step to identifying policies that may help the USDOT achieve its goal. MethodIn this paper we analyze fatality rates for different age cohorts in developed countries to better understand how road traffic fatality patterns vary across countries by age cohort. Using benchmarking analysis and comparative index analysis based on panel data modelling and data for selected years between 1990 and 2010, we compare changes in the rate of road traffic fatality over time, as well as the absolute level of road traffic fatality for six age groups in the US, with 15 other developed countries. Results-ConclusionsOur findings illustrate tremendous variations in road fatality rates (both in terms of the absolute values and the rates of improvement over time) among different age cohorts in all of the 16 countries. Looking specifically at the US, our analysis shows that safety improvements for Youngsters (15-17 years old) was much better than for other age groups, and closely tracked peer countries. In sharp contrast, Children (0-14 years old) and Seniors (+65 years old) in the US, fare very poorly when compared to peer countries. For example, in 2010, Children in the US were a stunning five times more likely to experience a road traffic fatality than Children in the UK. Practical ApplicationsThis startling statistic suggests an immediate need to explore further the causes and potential solutions to these disparities. This is especially important if countries, including the US, are to achieve the ambitious goals set out in Zero Vision initiatives.

Connected Vehicle Technology: An All Too Convenient Solution to Roadway Problems in the United States

Automobile accidents and roadway infrastructure problems are increasing in the United States. Specifically, 5.7 million automobile accidents were reported in 2013. The number of automobile accidents caused by lane drifting has increased over the past fifteen years, given the increased number of drivers on the road. The National Highway Traffic Safety Administration (NHTSA) and the United States Department of Transportation (USDOT) have developed a cumulative solution to these problems. Connected Vehicle technology is part of the USDOT’s “Intelligent Transportation Systems” (ITS) initiative. The ITS initiative targets automobile crash avoidance and better traffic flow through the use of automated technologies.[1] Id. at v.

Environmental Reviews and Case Studies: Setting Policy and Precedence: CREATE in Motion

The Chicago Region Environmental and Transportation Efficiency (CREATE) Program is a nationally prominent rail-infrastructure program. It is managed by the unique partnership of the United States Department of Transportation (DOT), the State of Illinois, the City of Chicago, Metra, Amtrak, Association of American Railroads, and six of the nation’s Class I freight railroads. The CREATE 75 th Street Corridor Improvement Project (CIP) received a National Environmental Policy Act (NEPA) Environmental Impact Statement (EIS) Record of Decision in September 2014. As a result of 75 th Street CIP and other completed preliminary engineering and project environmental reviews within the 70 rail-improvements program, CREATE has set a national-policy example with regard to mitigation under the environmental justice Executive Order (EO) 12898. This article provides some background on the CREATE Program and examines the development of the CREATE Environmental Justice Policy. It describes the impetus for creating the policy, namely noise impacts on low-income and minority populations resulting from the 75 th Street CIP and other CREATE Program rail projects. This article also discusses the extensive coordination among Federal and State agencies, among the public and private CREATE partners, and among Community Advisory Groups and residents, all of which led to the specific mitigations addressed in the CREATE environmental justice policy. The result of these encompassing efforts, led by Federal Highway Administration and the Illinois Department of Transportation’s Division of Public and Intermodal Transportation, is a precedent-setting framework for analyzing and, when necessary, mitigating the potential environmental justice impacts of the CREATE Program rail projects. The CREATE Environmental Justice Policy is precedent setting in a few ways: (a) it establishes policy where none currently exists and where existing highway-oriented policies do not seem appropriate or applicable; (b) it provides greater specificity with regard to what mitigation measures are “practicable” to address predicted noise impacts of CREATE Program rail projects on low-income and minority populations; (c) it clarifies the lead agencies’ intent to maintain the transportation linkage and focus when developing and evaluating practicable mitigation measures for other (i.e., non-noise) impacts; and (d) it helps assure the equity of the transportation investment by better balancing the distribution of burdens and benefits at the project level. This article identifies the steps, when considering disproportionately high and adverse impacts to low-income and/or minority populations, on how to evaluate other practicable mitigation measures with merit under EO 12898. This article also describes the lessons learned and the dialogue necessary to receive broad support from the CREATE partners for both needed rail improvements and additional mitigations to provide offsetting benefits and opportunities to enhance Chicago-area communities, neighborhoods, and residents’ quality of life. Environmental Practice 17: 256–269 (2015)

Assessment of Rut Depth Measurement Accuracy of Point-Based Rut Bar Systems Using Emerging 3D Line Laser Imaging Technology

Point-based rut bar systems are commonly used by transportation agencies. However, potential measurement errors exist in these systems because of the limited number of sample points (e.g. 3 to 31 points). Now, advanced sensing technology can acquire high-resolution transverse profiles of more than 4,000 points using 3D line laser imaging technology (termed the 3D line laser hereafter). This study, sponsored by the United States Department of Transportation (USDOT) Research and Innovative Technology Administration (RITA) program, is a) to explore the feasibility of using the 3D line laser to accurately and reliably measure rut depth, and b) to quantify the potential rut depth measurement errors using point-based rut bar systems. The rut depth measurement accuracy and repeatability of the 3D line laser were validated in laboratory and field tests. Results show that the absolute rut-depth measurement error is less than 3 mm, and, therefore, the transverse profiles acquired by the 3D line laser can be used to quantitatively evaluate the accuracy and reliability of point-based rut bar systems. Rut bar systems having 3 to 31 sensors were simulated using transverse profiles acquired by the 3D line laser. Test results show that the relative rut-depth measurement error generally decreases with the increasing number of laser sensors. However, the trend is unclear for rut bar systems with fewer sensors because the rut shape affects the rut depth measurement error more than the number of sensors. Thus, a 3-point rut bar system could outperform a 5-point system occasionally. Test results also show that the commonly used 3-point and 5-point rut bar systems can underestimate rut depth by 16% to 51% and 22% to 64%, respectively. The relative rut-depth measurement error is less than 10% only when the number of sensors is greater than 29.

Foundational Methodology for Creating Supplemental, FHWA-specific, Roadside Element Data Set, toward Using Big Data Techniques

The National Highway Traffic Safety Administration (NHTSA), an agency of the United States Department of Transportation (US DOT), provides crashworthiness data sets serving as a starting point for highway research. Although the information has provided guidance to safety researchers and decision-makers for vehicle damage and occupant injury research, crash environment fields have been inadequate to serve the growing surveillance burden placed upon the Federal Highway Administration (FHWA), another agency of the US DOT. Recent advances in NHTSA data reporting, however, have allowed for supplemental data acquisition, at no added cost.The 2008 Fatality Analysis Reporting System (FARS) release marked the first instance in which the geographical location was reported for fatal crashes and placed in the public domain. This opened a technological linkage with mapping tools to improve understanding of the crash environment. Further, improved photography introduced in the National Motor Vehicle Crash Causation Study and concurrent improvements in image capture for the National Automotive Sampling System Crashworthiness Data System provided better understanding of the crash scene.This paper provides the manual data extraction approach used in identifying candidate crashes and codification of roadside elements. Currently, FHWA is securing access to the Second Strategic Highway Research Program data, representing large stores of video. Leveraging recent FHWA Exploratory Advanced Research findings, in data mining and video capture, and lessons from the National Aeronautics and Space Administration and National Institutes of Health, the current project seeks to extend the manual approach to big data extraction.

A better path to progress on drunk driving.

Research finds significant impairment at 0.05 blood alcohol concentration (BAC). The world standard is 0.05. The National Transportation Safety Board (NTSB) has issued a strong recommendation for 0.05. So why isn't the highway safety community stepping up to lead the effort? There are three good reasons: Most studies, including those cited by Jim Fell and Bob Voas, find significant but not substantial impairment at 0.05 BAC. Unlike 0.08 BAC where all are intoxicated and are a primary threat to others on the road, Fell & Voas 1 state that ‘most’ are impaired. That makes simple substitution of the lower level to the very extensive array of criminal and administrative per se sanctions very problematic. It should be pointed out that not all countries with 0.05 have criminal penalties. Also, Hingson 2 and others have found, that Mothers Against Drunk Driving's (MADD) successful push for 0.08 BAC in all states save an estimated 600–800 lives per year, it is reasonable to estimate that the savings from 0.05 would be somewhat less. Such savings would be significant but finite. Law enforcement officers are the everyday heroes who get drunk drivers off the road, and everyone should be deeply concerned by the budget cuts they have faced in recent years. Increasing the number of violators without providing law enforcement with the resources they need would undercut deterrence, the primary doctrine MADD has successfully pursued since the findings of the Presidential Commission on Drunk Driving in 1983. Detection of 0.05 at sobriety checkpoints would also be more difficult. Legislatively, at the national level, the outlook is bleak. The benefits of 0.05 BAC presume enactment in all 50 states, which in turn presumes highway fund sanctions to force state action, which in turn presumes strong Congressional support which is non-existent and unlikely to change in the foreseeable future. MADD's Campaign to Eliminate Drunk Driving, launched in 2006, has an increasingly realistic target of virtually eliminating drunk driving at 0.08 BAC in the next 15 years. The four components of the Campaign are: committed support for high-visibility enforcement; enactment in all states of first conviction interlock laws; accelerated pursuit of advanced technologies that hold the real promise of not allowing the car to move when the driver is over 0.08 BAC; and continued aggressive efforts at increased public support. Since 2006, we have progressed from one state with first conviction interlock requirements at 0.08 to 20 states, with many more efforts pending and have made remarkable progress in developing a non-invasive in-vehicle alcohol detection system. We are profoundly grateful for the renewed commitments of support for pursuing advanced technology from National Highway Traffic Safety Administration (NHTSA) Administrator David Strickland and United States Department of Transportation (USDOT) Secretary Anthony Foxx. According to the Insurance Institute for Highway Safety, these technologies have the ability to save an estimated 7000 lives per year. Other initiatives for driverless cars would also have major implications for drunk driving. In conclusion, let me be clear. I do not oppose 0.05 BAC. I simply and strongly support the far better strategy of the Campaign to Eliminate Drunk Driving. The better approach on 0.05 is that all states should have, and many do, non-per se penalties at 0.05 for proven impairment rather than intoxicated driving. We all look forward to the day when there are no drunk drivers on the road. None.

A new access density definition and its correlation with crash rates by microscopic traffic simulation method

Better access management can improve highway safety by reducing potential crashes and conflicts. To make adequate access management decisions, it is essential to understand the impact of different access types on roadway safety, usually represented by the crash rate of a roadway segment. The objective of this paper is to propose a new access density definition reflecting the impact of traffic speed variation of different access types. The traffic speed variation was obtained from a microscopic traffic simulation software package TSIS-CORSIM. A sample roadway Temple Terrace Highway was selected to perform traffic simulation. Access Weight was obtained from traffic speed variation, and access density was obtained from access weight. The proposed access density was then compared with the existing definition by analyzing their correlations with crash rates on one suburban street in Temple Terrace, Florida. The comparison demonstrates that crash rates are more highly correlated with the proposed access density than that in the previous study, which is helpful for Federal Highway Administration (FHWA), United States Department of Transportation (USDOT), and transportation consulting companies to regulate the construction, management and design of roadway segments.

United States Department of Transportation

United States Department of Transportation

A mathematical modeling approach to resource allocation for railroad-highway crossing safety upgrades

State Departments of Transportation (S-DOT's) periodically allocate budget for safety upgrades at railroad-highway crossings. Efficient resource allocation is crucial for reducing accidents at railroad-highway crossings and increasing railroad as well as highway transportation safety. While a specific method is not restricted to S-DOT's, sorting type of procedures are recommended by the Federal Railroad Administration (FRA), United States Department of Transportation for the resource allocation problem. In this study, a generic mathematical model is proposed for the resource allocation problem for railroad-highway crossing safety upgrades. The proposed approach is compared to sorting based methods for safety upgrades of public at-grade railroad-highway crossings in Tennessee. The comparison shows that the proposed mathematical modeling approach is more efficient than sorting methods in reducing accidents and severity.

United States Department of Transportation (DOT) Human Factors Coordinating Committee (HFCC) Research Needs

The purpose of this discussion panel is to present the United States Department of Transportation (DOT) human factors research needs to the larger human factors research community. The DOT Human Factors Coordinating Committee (HFCC) serves as a multi-modal team with government-wide liaisons to promote human factors and to address crosscutting human factors issues in transportation. HFCC regularly conducts a survey of the DOT modal agencies and other federal agencies with a transportation focus (e.g., the National Transportation Safety Board) to identify cross-cutting DOT research needs. In this panel, the results of a recent survey will be presented with a discussion of how each modal agency is addressing these human factors areas of interest. Additionally, HFCC representatives from five modal agencies will review their current research efforts, discuss their anticipated future research needs, and address questions from the audience.

Machine Vision Condition Monitoring of Heavy-Axle Load Railcar Structural Underframe Components

To ensure the safe and efficient operation of the approximately 1.6 million freight cars (wagons) in the North American railroad network, the United States Department of Transportation (USDOT), Federal Railroad Administration (FRA) requires periodic inspection of railcars to detect structural damage and defects. Railcar structural underframe components, including the centre sill, sidesills, and crossbearers, are subject to fatigue cracking due to periodic and/or cyclic loading during service and other forms of damage. The current railcar inspection process is time-consuming and relies heavily on the acuity, knowledge, skill, and endurance of qualified inspection personnel to detect these defects. Consequently, technologies are under development to automate critical inspection tasks to improve their efficiency and effectiveness. Research was conducted to determine the feasibility of inspecting railcar underframe components using machine vision technology. A digital video system was developed to record images of railcar underframes and computer software was developed to identify components and assess their condition. Tests of the image recording system were conducted at several railroad maintenance facilities. The images collected there were used to develop several types of machine vision algorithms to analyse images of railcar underframes and assess the condition of certain structural components. The results suggest that machine vision technology, in conjunction with other automated systems and preventive maintenance strategies, has the potential to provide comprehensive and objective information pertaining to railcar underframe component condition, thereby improving utilization of inspection and repair resources and increasing safety and network efficiency.

Performance metrics for evaluating liquefied natural gas, vapor dispersion models

New performance metrics are necessary to quantify the inherent margins of safety 1 1 In this paper, margin of safety is an occupational safety phrase, and it is expressed as a ratio. in vapor dispersion models for liquefied natural gas (LNG) spills. Currently, vapor dispersion model calculations in the 49 Code of Federal Regulations, Part 193 as well as Standard 59A of the National Fire Protection Association (2001 edition) reduce the lower flammability limit (LFL) of methane in air by a safety factor of two (to 50% LFL) to ensure that flammable vapors do not extend beyond an LNG facility’s property line during an LNG spill. Yet, neither document explicitly states the additional distance or the additional confidence level this existing safety standard creates to separate the public from LNG vapors at 100 percent LFL within the facility vs. 50 percent LFL at the facility property line. Although researchers have successfully validated how vapor dispersion models calculate conservative buffer (exclusion) zones, their collective work did not readily explain to the general public the inherent margins of safety in these models. Havens and Spicer developed correlations to demonstrate how well DEGADIS 2 2 DEGADIS is a dense gas, vapor dispersion model that was developed in collaboration with the Gas Research Institute and the University of Arkansas. The United States Department of Transportation adopted DEGADIS in its LNG facility siting regulations within Part 193 of the 49 Code of Federal Regulations. predictions compared with field testing measurements in the late 80s ( Havens & Spicer, 1985). Their research also confirmed that peak gas concentrations exceeded time averaged measurements during some field trials as well as DEGADIS predictions. Then Hanna, Chang, and Strimaitis (1993) explained how several vapor dispersion models could be compared by calculating geometric mean bias and geometric variance and shared these validation results with the public. The works of the Havens and Hanna teams were also influential in explaining why the maximum concentration of methane in air at the property limits of an LNG facility should be 50 percent of its lower flammability limit during an LNG spill. Eleven years later, Chang and Hanna discussed how the relationships between fractional bias, geometric mean bias, geometric variance, and normalized mean square error could explain vapor dispersion model over and under prediction ( Chang & Hanna, 2004). Despite these successful efforts, there has been reluctance to embrace vapor dispersion model results, because exclusion zones are not described as creating margins of safety (i.e. additional separation distance) or higher confidence levels (i.e. a likelihood of being correct) that protect the public. This paper proposes an improved performance metric to evaluate the validity of vapor dispersion models and a statistical methodology to determine the confidence level and the inherent margin of safety in calculating vapor dispersion exclusion zones. Descriptions of the new metric and methodology are presented in this document for the DEGADIS vapor dispersion model, together with example calculations.

Legislating child restraint usage –Its effect on self-reported child restraint use rates in a central city

Objective To assess the effect of the newly enacted child passenger safety law, Wisconsin Act 106, on self-report of proper restraint usage of children in Milwaukee's central city population. Method A prospective, non-randomized study design was used. The settings used were (a) a pediatric urban health center, and (b) two Women, Infants and Children offices in Milwaukee, Wisconsin. Participants included 11,566 surveys collected over 18 months that spanned the pre-legislation and post-legislation time periods from February 2006 through August 2008. Results The study set out to assess appropriate child passenger restraint. The results showed that the changes in adjusted proper restraint usage rates for infants between the pre-law, grace period, and post-fine periods were 94%, 94%, and 94% respectively. For children 1–3 years old, the adjusted proper usage rates were 65%, 63%, and 59%, respectively. And for children 4–7 years old, the rates were 43%, 44% and 42%, respectively. There was a significant increase in premature booster seat use in children who should have been restrained in a rear- or forward-facing car seat (10% pre-law, 12% grace period, 20% post-fine; p < 0.0005). There was no statistically significant change over time in unrestrained children (2.1%, 1.7%, 1.7%, p = 0.7, respectively). Conclusions The passage of a strengthened child passenger safety law with fines did not significantly improve appropriate restraint use for 0–7 year olds, and appropriate use in 1–7 year olds remained suboptimal with a majority of urban children inappropriately restrained. Although the number of unrestrained children decreased, we identified an unintended consequence of the legislation – a significant increase in the rate of premature belt-positioning booster seat use among poor, urban children. Impact on Industry The design of child restraint systems maximizes protection of the child. Increasing reports of misuse is a call to those who manufacture these child passenger restraints to improve advertising and marketing to the correct age group, ease of installation, and mechanisms to prevent incorrect safety strap and harness placement. To ensure accurate and consistent use on every trip, car seat manufacturers must ensure that best practice recommendations for use as well as age, weight, and height be clearly specified on each child restraint. The authors support the United States Department of Transportation's new consumer program that will assist caregivers in identifying the child seat that will fit in their vehicle. In addition, due to the increase in premature graduation of children into belt-positioning booster seats noted as a result of legislation, promoting and marketing booster seat use for children less than 40 pounds should not be accepted. Child passenger safety technicians must continue to promote best practice recommendations for child passenger restraint use and encourage other community leaders to do the same.

Frequency analysis of hazardous material transportation incidents as a function of distance from origin to incident location

According to the United States Department of Transportation (USDOT), more than 3.1 billion tons of hazardous materials (HazMat) are shipped within the United States annually. This averages to about 800,000 individual shipments of HazMat per day, of which 300,000 are shipments of petroleum/flammable–combustible liquids. This paper presents a temporal trend study (1995–2004) of 2145 HazMat incidents occurring through the transportation of flammable/combustible liquids. The study also correlates between HazMat incidents and distances between shipment origin and incident location. These distances attained through great circle calculations since the data compilation did not allow for the identification of specific routes taken in commodity transport. Findings of this study illustrate a bimodal distribution of frequency as a function of the logarithm of the Distance with first mode (less than 105 miles) mean of 24 [km] and second mode mean of 1061 [km]. Additionally, transport phase introduced no significance to the distribution of frequencies.

Digital map as a virtual sensor – dynamic road curve reconstruction for a curve speed assistant

While digital map has been applied to many advanced driver assistance system applications, one critical attribute – road/lane curvature—is not available in the existing digital maps. Curvature derivation using splines is a well-known method in the computer graphics modelling community; however, it was also found that the direct application of the spline method is often not appropriate for real-time safety applications due to the resultant discontinuities in the curvature estimates and the lack of robustness against map data errors [CAMP, Enhanced digital mapping project final report, United States Department of Transportation, Washington, DC, 2004]. This paper presents a method to reconstruct road curvature attributes in real time using digital map data based on the proposed circle centre search and circle selection algorithms. Simulation and experimental results demonstrated that the proposed method can deliver curvature estimates that meet the desired accuracy. The method was also applied to the curve over-speed warning system in an on-going research project: Vehicle Infrastructure Integration—California. Some preliminary experimental results are also presented in this paper.

Simple Engine Models for VII-Enabled In-Vehicle Applications

The rapid development of intervehicular communication technology, coupled with the United States department of transportation (USDOT)'s vehicle infrastructure integration (VII) initiative, will soon enable a new class of in-vehicle applications such as cooperative driving assistance systems (CDASs). An engine model with reasonable accuracy and excellent computational efficiency is called for to facilitate the development of such systems. This paper presents and formulates three candidate models (Models I, II, and III), among which Model I is an existing one, and the other two are new. Their performances are evaluated based on a system of metrics including accuracy, accessibility, computational efficiency, formulation, and the need for calibration. Overall, Model II outperforms the other two and appears promising to fit the need of the particular application.

Acute Respiratory Infections in a Recently Arrived Traveler to Your Part of the World*

Many acute infectious pulmonary diseases have incubation periods that are long enough for travelers to have symptoms after returning home to a health-care system that is not familiar with “foreign” infections. Respiratory infections have a relatively limited repertoire of clinical manifestations, so that there is often nothing characteristic enough about a specific infection to make the diagnosis obvious. Thus, the pathway to the diagnosis of infections that are not endemic in a region relies heavily on taking a thorough history of both itinerary and of specific exposures. One important caveat is that on occasion, the history of a recent trip creates an element of “tunnel vision” in the evaluating health-care provider. It is tempting to relate a person's problem to that recent trip; however, when evaluating recent returnees, it is always important to remember that the travel may have nothing to do with the patient's presentation. Recent travel may add diagnostic considerations to the list of possibilities, but an astute clinician must not disregard the possibility that the patient's illness has nothing to do with the recent trip.

Determinants of motor carrier safety technology adoption

In this paper, we investigate the organizational determinants of safety technology adoption. To shed light on this important question, we develop and test nine hypotheses. Results are based on a national survey of motor carriers sponsored by the United States Department of Transportation. Using a Poisson regression model, we find statistical support for seven hypotheses. A key finding is that prior safety performance influences a firm’s adoption of safety technologies. Additionally, a firm’s optimism about the potential for safety technologies, its technological innovativeness, and its level of comfort with new technologies contribute to its safety technology adoption decisions.