Is It Safer to Fly or Drive?

In attempts to soothe the nascent fear of the scheduled airline traveler, passengers waiting takeoff are sometimes reminded of the cliche that they may have already completed the most dangerous part of their trip — the drive to the airport. The objective of this paper is to communicate under what conditions air travel is indeed safer than highway travel and vice versa. The conventional wisdom among risk communicators that air travel is so much safer than car travel arises from the most widely quoted death rates per billion miles for each — 0.6 for air compared to 24 for road. There are three reasons why such an unqualified comparison of aggregated fatality rates is inappropriate. First, the airline rate is passenger fatalities per passenger mile, whereas the road rate is all fatalities (any occupants, pedestrians, etc.) per vehicle mile. Second, road travel that competes with air travel is on the rural interstate system, not on average roads. Third, driver and vehicle characteristics, and driver behavior, lead to car-driver risks that vary over a wide range. Expressions derived to compare risk for drivers with given characteristics to those on airline trips of given distance showed that 40-year-old, belted, alcohol-free drivers of cars 700 pounds heavier than average are slightly less likely to be killed in 600 miles of rural interstate driving than in airline trips of the same length. Compared to this driver, 18-year-old, unbelted, intoxicated, male drivers of cars 700 pounds lighter than average have a risk over 1000 times greater. Furthermore, it is shown that the cliche above is untrue for a group of drivers having the age distribution of airline passengers.     

Urban Risks of Truck Transport of Radioactive Material

Truck transport of radioactive material (RAM), e.g., spent nuclear fuel (SNF), normally maximizes use of Interstate highways, which are safer and more efficient for truck transport in general. In the estimation of transportation risks, population bordering a route is a direct factor in determining consequences and an indirect factor in determining exposure times, accident probabilities and severities, and other parameters. Proposals to transport RAM may draw intense resistance from "stakeholders" based on concern for population concentrations along urban segments but the length of a route segment is also a determinative factor in estimating the transport risks. To quantify the relative importance of these two factors, a potential route for transport of SNF (strict use of Interstate highways) was selected and compared with a modified version that bypassed urban areas. The results suggest that emphasis on Interstate highways minimizes total route and urban segment risks.     

Should Persons with Diabetes Be Licensed to Drive Trucks?—Risk Management

How should a regulatory agency interpret a risk analysis that concludes there is a small increase in risk? The agency must decide on behalf of society whether the increased risk is large enough to justify banning the risky activity or taking some other step to lessen the risks. In a companion paper (Songer et al.), we conclude that licensing insulin using persons to drive commercial motor vehicles in interstate commerce would result in 42 additional crashes each year. Here we address risk management issues by interpreting the number of additional crashes and the relative risks of the prospective handicapped drivers. Are the number of additional crashes (42) significant? Is the increase in the annual crash risk (from 0.00785 to 0.032 for non-insulin dependent and 0.048 for insulin dependent persons) significant? Are the relative risks significant for all insulin using drivers (4.7)? For drivers with a history of severe hypoglycemic reactions (19.8)? How should society tradeoff risk increases for increases in opportunity for these handicapped persons? We review other social decisions concerning highway safety: Accepting the increasing risks of letting 16 year olds drive, allowing extremely light cars, allowing some unsafe highways, and allowing extremely unsafe driving conditions at some times of day. We conclude that the additional risks from insulin using persons are well within the current accepted range of risks. Currently, 70% of states permit insulin using persons to drive trucks within their state. Nonetheless, the social cost, due to fatalities, injuries, and property damage from allowing a person with a history of severe hypoglycemic reactions to drive is more than $19,700 per year.     

Understanding and Reducing Inconsistency in Seatbelt‐Use Decisions: Findings from a Cardinal Decision Issue Perspective

This article has two aims. The first is to present results that partly explain why some automobile drivers choose to use their seatbelts only part time, thereby exposing themselves to unnecessary risk. The second is to offer and illustrate the “cardinal decision issue perspective”⁽¹⁾ as a tool for guiding research and development efforts that focus on complex real‐life decision behaviors that can entail wide varieties of risk, including but not limited to inconsistent seatbelt use. Each of 24 young male participants drove an instrumented vehicle equipped to record continuously seatbelt use as well as other driving data. After all trips were finished, each participant completed an interview designed to reconstruct how he made randomly selected seatbelt‐use decisions under specified conditions. The interview also examined whether and how drivers established “decision policies” regarding seatbelt use. Such policies were good predictors of inconsistent seatbelt use. Drivers who had previously adopted policies calling for consistent seatbelt use were significantly more likely than others to actually drive belted. Meta‐decisions about seatbelt policy adoption appeared to rest on factors such as whether the driver had ever been asked to consider selecting a policy. Whether a driver made an ad hoc, on‐the‐spot seatbelt‐use decision was associated with a perceived need to make such a decision. Finally, participants with full‐time policies were especially likely to deploy their seatbelts by default, without recognizing the need to decide about belt use on a trip‐by‐trip basis. We end with recommendations for reducing inconsistencies in seatbelt use in actual practice.     

The Risks of Licensing Persons with Diabetes to Drive Trucks

The 1990 Americans with Disabilities Act forbids employers to bar disabled persons from jobs unless employers can show the disabled person cannot perform the tasks. The Federal Highway Administration will not license persons with diabetes mellitus to drive commercial motor vehicles in interstate commerce. These individuals may experience severe hypoglycemia, greatly increasing their risk of losing control of the truck. This prohibition is currently being reexamined. We describe the disease process leading to severe hypoglycemia and its physical manifestations. To quantify the risks of licensing persons with diabetes to use insulin, we first estimate the number of potential insulin-using drivers. We estimate that 1420 insulin-using persons would seek licenses in the United States if they were permitted to do so (920 noninuslin dependent and 500 insulin dependent). Next, we estimate the annual incidence of mild and severe hypoglycemia in these populations. The third step is to estimate the number of hypoglycemic episodes while driving. Estimating the likelihood of a crash due to a mild or severe hypoglycemic episode is the fourth step. We estimate that an additional 42 crashes each year would occur if insulin using persons were licensed to drive commercial motor vehicles in interstate commerce (20 from insulin dependent and 22 from non-insulin dependent drivers).     

Traffic Accidents and Convictions: Group Totals Versus Rate per Kilometer Driven

Using group totals, young drivers, male drivers, and especially young male drivers are substantially over-represented in terms of both traffic accidents and traffic-related convictions. On the other hand, when accidents and convictions are considered in terms of their rates while the person is actually driving, older drivers and female drivers gain in importance, with the female drivers' traffic accident rate and rates for some convictions exceeding the male drivers' rates. Similarly, the older drivers' accident rate and rates on some convictions exceeded the younger drivers' rates when considered in terms of driving exposure. In addition, these findings lead one to speculate that recent driving exposure more than driver age is the central factor in traffic accident involvement. The implications for policy makers and educators are clear. Although young male drivers are undeniably a legitimate focus for traffic accident countermeasures, they should not be targeted at the expense of drivers who drive less but have as high or higher accident rates—female and older drivers.     

A Causal Analysis of Large Vehicle Accidents Through Fault-Tree Analysis

Recent trends indicate that vehicle miles traveled for large trucks is increasing at a higher rate than for other vehicles. The resulting competition between large trucks and other vehicles for highway space can be expected to result in more multivehicle collisions involving large trucks. This paper presents the result of an investigation of the causes and the mechanism related to large vehicle accidents. A fault-tree analysis of large vehicle accidents identifies the individual roles played by driver, vehicle, and environmental factors, as well as their interactions in the accident mechanism. Using accident data for 1984-1986, the probabilities for different basic events in the fault tree were assessed. The most likely events leading to a large vehicle accident, as well as the most effective counter measures, were then identified. The result indicate that the most prevalent form of accidents due to driver-related failures is when a normal driver makes an error in judgment and is unsuccessful in his or her evasive action. For vehicle-related failures, the predominant type of failure is equipment failure, and for environmental-related failures, excessive demand on driver and vehicle performance created by the environmental or roadway factors.     

Measuring dynamic efficiency of highway maintenance operations

In this paper we discuss a dynamic efficiency measurement model for evaluating the performance of highway maintenance policies where the inter-temporal dependencies between consumption of inputs (i.e., maintenance budget) and realization of outputs (i.e., improvement in road condition) are explicitly captured. We build on a micro representation of pavement deterioration and renewal processes and study the impact of the allocation of scarce maintenance budgets over time. We provide a measure of efficiency that contrasts the optimized budget allocations to the actual ones. The developed model is then applied to an empirical dataset of pavement condition and maintenance expenditures over the years 2002 to 2008 corresponding to seventeen miles of interstate highway that lay in one of the counties in the state of Virginia, USA. The policies that were found through optimization showed that road authorities should give higher priorities to preventive maintenance than corrective maintenance. In essence, by applying preventive maintenance, the road authorities can effectively decrease the need for future corrective maintenance while spending less overall.     

Do Drivers of Small Cars Take Less Risk in Everyday Driving?

Previously reported observed data on risky everyday driving are brought together and reanalyzed in order to focus on the relation between risky driving and the size of the car being driven, as indicated by car mass. The measures of risky driving include separation between vehicles in heavy freeway traffic and speed on a two lane road. Observed seat belt use provides a third measure of driver risk. Confounding effects arising from the observed association between car mass and driver age are taken into account by segmenting the data into three driver age groups. Driver risk taking is found to increase with increasing car mass for each of these three aspects of everyday driving. The implications of these results with respect to driver fatality rates are discussed in terms of a simple model relating observed risky driving to the likelihood of involvement in a severe crash.     

Reverse logistics drivers: empirical evidence from a case study in an emerging economy

Academic and corporate interest in reverse logistics (RL) has risen considerably in recent years. In this context, the objective of this study was to identify the drivers that enable RL practice in an emerging economy. Firstly, international peer-reviewed publications on RL were used to develop a RL environment framework representing the main RL internal and external influences. Secondly, a case-based research was conducted in a large manufacturing company located in Southern Brazil. The results indicated that the most cited driver in the RL literature, the government and legislation, was not a main influence on the studied company. Environmental legislation is still limited in the country and struggles to provide incentives to increase materials recycling. An economic factor related to materials value recovery was also found to drive the backward flow. Finally, knowledge of the RL driving forces may support industries to better implement and manage reverse flows and to bridge the gap between existing and future solutions for reverse supply chains.     

Out of the Frying Pan into the Fire: Behavioral Reactions to Terrorist Attacks

A low-probability, high-damage event in which many people are killed at one point of time is called a dread risk. Dread risks can cause direct damage and, in addition, indirect damage mediated though the minds of citizens. I analyze the behavioral reactions of Americans to the terrorist attacks on September 11, 2001, and provide evidence for the dread hypothesis: (i) Americans reduced their air travel after the attack; (ii) for a period of one year following the attacks, interstate highway travel increased, suggesting that a proportion of those who did not fly instead drove to their destination; and (iii) for the same period, in each month the number of fatal highway crashes exceeded the base line of the previous years. An estimated 1,500 Americans died on the road in the attempt to avoid the fate of the passengers who were killed in the four fatal flights.     

Effects of neuroticism, extraversion, circadian type and age on reported driver stress

Studies have examined effects of various personality variables, including extraversion and neuroticism, as well as age, on driver stress. However, the effect of the morningness-eveningness dimension (circadian type) on reported driver stress among commuters has not been investigated. This study aimed to assess the influence of circadian type as well as extraversion, neuroticism and age on driver stress. Participants were 101 Australian university administrative staff who completed the Eysenck Personality Questionnaire-Revised, the Morningness-Eveningness Questionnaire, and also morning and evening driving diaries as a state measure of driver stress each weekday for one week. Two standard multiple regressions assessed whether neuroticism, extraversion, circadian type and age predicted reported driver stress for morning and evening drives. Neuroticism, circadian type, and age predicted reported driver stress in the mornings but age mainly predicted driver stress in the evenings. A repeated measures ANOVA isolated differences between circadian types for weekday mornings and evenings. Reported driver stress differed for day of week and time of day according to circadian type. The three-way interaction suggested that driver stress is influenced by circadian type and that factors influence driver stress differentially between mornings and evenings. Circadian type appears to influence when driver stress affects individuals.     

粒子群优化的模糊聚类方法在车辆行驶工况中的应用

本文研究了粒子群优化的模糊聚类方法在车辆行驶工况中的应用。采用主成分分析方法将众多反映车辆行驶工况特征的运动学片段特征值进行压缩,用粒子群优化的模糊聚类方法对运动学片段的前三个主成分得分进行聚类,通过Matlab编程将上述理论用于合肥市典型道路行驶工况的构建和分析,按时间比例选取合适片段拟合代表性工况,并将代表性工况和采用K均值聚类法及模糊C均值聚类方法拟合的工况进行对比分析。研究结果表明,将粒子群优化的模糊聚类方法应用到工况的构建中可以有效地提高构建精度。     

Effects of neuroticism,extraversion, circadian type and age on reported driver stress

Studies have examined effects of various personality variables, including extraversion and neuroticism, as well as age, on driver stress. However, the effect of the morningness-eveningness dimension (circadian type) on reported driver stress among commuters has not been investigated. This study aimed to assess the influence of circadian type as well as extraversion, neuroticism and age on driver stress. Participants were 101 Australian university administrative staff who completed the Eysenck Personality Questionnaire-Revised, the Morningness-Eveningness Questionnaire, and also morning and evening driving diaries as a state measure of driver stress each weekday for one week. Two standard multiple regressions assessed whether neuroticism, extraversion, circadian type and age predicted reported driver stress for morning and evening drives. Neuroticism, circadian type, and age predicted reported driver stress in the mornings but age mainly predicted driver stress in the evenings. A repeated measures ANOVA isolated differences between circadian types for weekday mornings and evenings. Reported driver stress differed for day of week and time of day according to circadian type. The three-way interaction suggested that driver stress is influenced by circadian type and that factors influence driver stress differentially between mornings and evenings. Circadian type appears to influence when driver stress affects individuals.     

The effects of driving age, driver education, and curfew laws on traffic fatalities of 15-17 year olds

This study examines the effect of state driving age, learning permit, driver's education, and curfew laws on 15-17-year-old driver fatality rates. A multivariate regression model is estimated for 47 states and nine years. The minimum legal driving age and curfew laws are found to be important determinants of fatalities. Driver's education and learning permits have smaller effects. The relationship between rates of licensure and driving age, education, and curfew laws is also examined. In each case, a more restrictive policy is found to reduce licensure of 15-17 year olds. The results suggest that the imposition of curfew laws and higher minimum driving ages are particularly effective traffic safety policies.     

Changes in Product Attributes and Costs as Drivers of New Product Diffusion and Substitution

Diffusion theory has typically focused on how communication, internal or external to a social system, leads to adoptions and diffusion of an innovation. We develop a diffusion and substitution model based on a somewhat different perspective. In some cases, progressive improvements in product attributes and/or continual cost reduction seem to be a key driver of the diffusion process. For example, after introduction of the 5.25‐inch disk drive, its capacity continually increased, and accordingly, so did customer willingness‐to‐pay. Our model is based on a linear reservation price framework, in which a product is described by its depth (defined as the difference between a product̂s maximum reservation price and its production cost), and its breadth (related to the slope of its reservation price curve), indicating how broadly it appeals across various customer segments. Because of changes in product depths and breadths over time, customers who previously preferred the old product may later prefer the new product, thus creating the diffusion process. While the Bass model describes diffusion as a function of the coefficients of innovation and imitation, in our model, it is described by the coefficients of depth and breadth (the rates of change in relative depth and breadth), along with an S‐coefficient that we associate with the technology S‐curve. We fit our model to data from the disk‐drive and the microprocessor industries.     

A PAVEMENT MANAGEMENT DECISION SUPPORT SYSTEM

We present a pavement management expert system developed by the University of Wisconsin-Madison and implemented within a geographical information system for the Wisconsin Department of Transportation. The system uses pavement data regularly collected on the state's 12,000 miles of highway to assist engineers, planners, and budget analysts' management decisions about pavements to be included in 6-year improvement and 3-year maintenance programs. The system has a three-layer architecture. The lowest level suggests treatments for each of a large number of small segments of highway. The middle layer aggregates segments, suggests alternative treatments, and estimates the cost of each. The top layer prioritizes the projects and incorporates them into intermediate-range plans. The geographical information system environment enables integration of existing databases within the system using a topologically structured geographic database and specialized software.     

A Polynomial Time Approximation Scheme for the Problem of Interconnecting Highways

The objective of the Interconnecting Highways problem is to construct roads of minimum total length to interconnect n given highways under the constraint that the roads can intersect each highway only at one point in a designated interval which is a line segment. We present a polynomial time approximation scheme for this problem by applying Arora's framework (Arora, 1998; also available from http:www.cs.princeton.edu/~arora). For every fixed c > 1 and given any n line segments in the plane, a randomized version of the scheme finds a -approximation to the optimal cost in O(n ^O(c)log(n) time.     

Age and Gender Differences in Perceived Accident Likelihood and Driver Competences

Road traffic accident involvement rates show clear age and gender differences which may in part be accounted for by differences in risk perception and perceptions of driving competence. The present study extends and replicates that of Matthews and Moran (1986). Young (18–30 years) and older (45–60 years) male and female drivers responded to a questionnaire on perceived accident risk and driving competence (judgment and skill) with respect to themselves and four target groups, and also rated a series of videotaped driving sequences with respect to likelihood of accident occurrence and perceived driving competence. Results showed that effects of rater characteristics were generally confined to the questionnaire. Younger males were perceived as most likely to experience an accident and were judged to be lower than other groups in driving competence. Younger groups showed little bias against older groups and vice versa , but gender-related bias was apparent. The findings of Matthews and Moran were generally confirmed. The results are discussed with reference to four main issues: (1) demographic bias effects—which are generally weak; (2) stereotyping on the basis of gender and/or age of driver; (3) group-specific bias; (4) self-appraisal bias.     

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