Car Occupant Life Expectancy: Car Mass and Seat Belt Effects

Average human life expectancies for the U.S. resident population are calculated using tabulated population and survival rate data. These life expectancies are recalculated assuming elimination of various types of motor vehicle fatalities using Fatal Accident Reporting System (FARS) data. The differences between the original and recalculated values provide estimates of life expectancy reductions due to the motor vehicle fatalities. These estimates are combined with prior work relating the likelihood of an occupant fatality to car mass, so that reductions in life expectancy are determined as a function of car mass. The estimates of life expectancy reductions are also used to determine the effect of seat belt use on life expectancy. The estimates, which are based on data for 1978, assume that survival rates remain unchanged. Estimates of the changes in life expectancy associated with switching from a large (1800 kg) car to a small (900 kg) car, and switching from not using to using a seat belt are presented as functions of the age at which an individual makes the switch.     

Effects of Increased Auto Safety Belt Use Levels on Fatalities

To reduce the annual toll of highway deaths, more than 30 states have passed laws mandating the use of safety belts. All have been effective at raising safety belt use; equipped with different provisions and enforced with unequal care, however, they have done so to different degrees. The article estimates the relationship between attained belt use and fatalities averted. Monthly 1982-1986 fatality, collision, belt use, and other data from 64 areas in nine states were collected, then analyzed using a Poisson multiple regression model. The analysis indicates that an increase in belt use from 14-40% averts about 13% of fatalities; a more pronounced increase to 50% averts about 18%. An increase from 50-75% averts about 16% of remaining fatalities. Three significant conclusions emerge. First, previous estimates appear to have understated, in general, the overall effectiveness of belt use laws. Second, the benefits of programs to boost safety belt use in this country from its current level of about 50% to up to 75%, estimated on the basis of more direct evidence from U.S. data than previously available, appear to be very large. Third, Poisson and other multiple regression models including explicit allowance for other causal factors can usefully complement other statistical approaches in traffic safety studies.     

The Case against Commercial Antivirus Software: Risk Homeostasis and Information Problems in Cybersecurity

New cybersecurity technologies, such as commercial antivirus software (AV), sometimes fail to deliver on their promised benefits. This article develops and tests a revised version of risk homeostasis theory, which suggests that new cybersecurity technologies can sometimes have ill effects on security outcomes in the short run and little-to-no effect over the long run. It tests the preliminary plausibility of four predictions from the revised risk homeostasis theory using new survey data from 1,072 respondents. The estimations suggest the plausible operation of a number of risk homeostasis dynamics: (1) commercial AV users are significantly more likely to self-report a cybersecurity event in the past year than nonusers, even after correcting for potential reverse causality and informational mechanisms; (2) nonusers become somewhat less likely to self-report a cybersecurity event as the perceived riskiness of various e-mail-based behaviors increases, while commercial AV users do not; (3) the negative short-run effect of commercial AV use on cybersecurity outcomes fade over time at a predicted rate of about 7.03 percentage points per year of use; and (4) after five years of use, commercial AV users are statistically indistinguishable from nonusers in terms of their probability of self-reporting a cybersecurity event as perceptions of risky e-mail-based behaviors increase.     

Motivating Auto Safety Belt Wearing in Industrial Settings:

Employees at an industrial plant (n = 141) participated in 40-minute safety belt "awareness sessions," which for some groups included opportunities to sign buckle up pledge cards. The duration of the pledge period was one week, one month, or three months for different groups of approximately 35 employees each. The awareness sessions, alone or with pledge cards, yielded a three-fold increase in safety belt use (from approximately 20% to 60%), which was sustained over the 13 weeks of post-session observation. While most employees signed pledge cards regardless of the pledge duration, pledging did not produce greater increases in safetey belt use than the awareness sessions without pledge cards. Further, pledge duration had no differential effect on likelihood of signing, or subsequent compliance. The usual white/blue-collar difference was found, with white-collar employees showing higher rates of safety belt use throughout the study. The results suggest strongly that an "intrinsic control" strategy of raising awareness and increasing personal commitment to buckle up can substantially increase safety belt use. The application of this approach as a cost-effective component of an overall program to increase safety belt use is discussed.     

A Risk-Based Method for Modeling Traffic Fatalities

We describe a risk-based analytical framework for estimating traffic fatalities that combines the probability of a crash and the probability of fatality in the event of a crash. As an illustrative application, we use the methodology to explore the role of vehicle mix and vehicle prevalence on long-run fatality trends for a range of transportation growth scenarios that may be relevant to developing societies. We assume crash rates between different road users are proportional to their roadway use and estimate case fatality ratios (CFRs) for the different vehicle-vehicle and vehicle-pedestrian combinations. We find that in the absence of road safety interventions, the historical trend of initially rising and then falling fatalities observed in industrialized nations occurred only if motorization was through car ownership. In all other cases studied (scenarios dominated by scooter use, bus use, and mixed use), traffic fatalities rose monotonically. Fatalities per vehicle had a falling trend similar to that observed in historical data from industrialized nations. Regional adaptations of the model validated with local data can be used to evaluate the impacts of transportation planning and safety interventions, such as helmets, seat belts, and enforcement of traffic laws, on traffic fatalities.     

Child Passenger Safety: Decisions about Seating Location, Airbag Exposure, and Restraint Use

The installation of passenger-side airbags in new vehicles complicates efforts to maximize child safety in motor vehicle crashes. It has been recommended by both public and private organizations that children sit in the rear seat with proper restraint to achieve maximum safety. Drivers now need to decide whether a child should be restrained, where the child should be seated (front versus rear), and whether the child should be seated in front of a passenger-side airbag. This research was undertaken to determine which choice minimizes the risk of fatality to children. Using data from the U.S. Fatality Analysis Reporting System for calendar years 1989 to 1998, fatal vehicle crashes with child passengers younger than 13 years were analyzed. The effectiveness of passenger-side airbags and rear seating for children, by age category and restraint use, was estimated using the double-pair comparison method. For each of four age categories, the fatality risk of each possible combination of restraint use, seating location, and airbag presence was also estimated using logistic regression. Passenger airbags were associated with an increase in child fatality risk of 31% for restrained children, and 84% for unrestrained children. Passenger airbags did appear to offer protection to restrained 9- to 12-year-old children. Restraint use and rear seating were associated with statistically significant reductions in the odds of a child dying in a crash. In order to minimize child fatality risk, parents should seat children in the rear of the vehicle while using the proper child restraint system, especially in vehicles with passenger airbags. These findings support current public education efforts in the United States.     

Validating Benefit and Cost Estimates: The Case of Airbag Regulation

Preregulation estimates of benefits and costs are rarely validated after regulations are implemented. This article performs such a validation for the mandatory automobile airbag requirement. We found that the original 1984 model used to estimate benefits became invalid when 1997 values were input into that 1984 model. However, using a published 1997 cost-effectiveness model, we demonstrate, by replacing the model inputs with the values from 1984, that the 1997 cost-effectiveness ratios, based on real-world crash data and tear-down cost data, are less attractive than what would have been originally anticipated. The three most important errors in the 1984 input values are identified: the overestimation of airbag effectiveness, the overestimation of baseline fatality/injury rates, and the underestimation of manual safety belt use. This case study, which suggests that airbags are a reasonable investment in safety, shows that the regulatory analysis tools do not always produce findings that are biased against health, safety, and environmental regulation. Future validation studies of health, safety, and environmental regulation should focus on validation of benefit and risk estimates, areas where we found significant error, as well as on cost estimates.     

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.     

Compressed Natural Gas Bus Safety: A Quantitative Risk Assessment

This study assesses the fire safety risks associated with compressed natural gas (CNG) vehicle systems, comprising primarily a typical school bus and supporting fuel infrastructure. The study determines the sensitivity of the results to variations in component failure rates and consequences of fire events. The components and subsystems that contribute most to fire safety risk are determined. Finally, the results are compared to fire risks of the present generation of diesel-fueled school buses. Direct computation of the safety risks associated with diesel-powered vehicles is possible because these are mature technologies for which historical performance data are available. Because of limited experience, fatal accident data for CNG bus fleets are minimal. Therefore, this study uses the probabilistic risk assessment (PRA) approach to model and predict fire safety risk of CNG buses. Generic failure data, engineering judgments, and assumptions are used in this study. This study predicts the mean fire fatality risk for typical CNG buses as approximately 0.23 fatalities per 100-million miles for all people involved, including bus passengers. The study estimates mean values of 0.16 fatalities per 100-million miles for bus passengers only. Based on historical data, diesel school bus mean fire fatality risk is 0.091 and 0.0007 per 100-million miles for all people and bus passengers, respectively. One can therefore conclude that CNG buses are more prone to fire fatality risk by 2.5 times that of diesel buses, with the bus passengers being more at risk by over two orders of magnitude. The study estimates a mean fire risk frequency of 2.2 x 10(-5) fatalities/bus per year. The 5% and 95% uncertainty bounds are 9.1 x 10(-6) and 4.0 x 10(-5), respectively. The risk result was found to be affected most by failure rates of pressure relief valves, CNG cylinders, and fuel piping.     

Estimated Risk of Occupational Fatalities Associated with Hazardous Waste Site Remediation

This study presents a method to assess short term traumatic fatality risks for workers involved in hazardous waste site remediation to provide a quantitative, rather than qualitative, basis for evaluating occupational exposures in remediation feasibility studies. Occupational employment and fatality data for the years 1979–1981 and 1983 were compiled from Bureau of Labor Statistics data for 11 states. These data were analyzed for 17 occupations associated with three common remediation alternatives: excavation and landfill, capping, and capping plus slurry wall. The two occupations with the highest death rates, truck driver and laborer, contributed most to total exposure hours in each alternative. Weighted average death rates were produced for each alternative and multiplied by respective total person-years of exposure. The resultant expected number of fatalities was converted, using the Poisson distribution, to the risk of experiencing at least one fatality, as follows: 0.149 for excavation and landfill, 0.012 for capping, and 0.014 for capping plus slurry wall. These risks were discussed in light of the need to obtain more reliable and comprehensive data than are currently available on the occupational safety and health risks associated with hazardous waste site remediation and the need for a more scientific, quantitative approach to remediation decisions involving risks to workers.     

Discount Rates in Risk Versus Money and Money Versus Money Tradeoffs

We use data from a survey of residents of five Italian cities conducted in late spring 2004 to estimate the discount rates implicit in (1) money versus future risk reductions and (2) money versus money tradeoffs. We find that the mean personal discount rate is 0.3-1.7% in (1) and 8.7% in (2). The latter is lower than the discount rates estimated in comparable situations in many recent studies, greater than market interest rates in Italy at the time, and exhibits modest variation with age and gender. The discount rate implicit in money versus risk tradeoffs is within the range of estimates from studies in the United States and Europe, and does not depend on observable individual characteristics. We use split samples to investigate whether a completely abstract risk reduction - one where the risk reduction delivery has been stripped of all specifics, so that respondents should focus on the risks without being distracted by details - results in WTP and discount figures comparable to those from an identified delivery mechanism (a medical test). We find that while WTP for an immediate risk reduction is 42-73% higher with the abstract risk reduction, the discount rate in the money versus risk tradeoffs and the variance of the error term in the WTP equation are the same across the two variants of the questionnaire.     

Risk-Informed Requirements for Design and Assessment of Structures Under Temporary Use

The relatively high failure rates, with important consequences in many cases, suggest that the implicitly acceptable risk levels corresponding to temporary civil engineering structures and activities might exceed the bounds of normally acceptable levels associated with different societal activities. Among other reasons, this may be attributed to the lack of a rational approach for the assessment of risks associated with the different technologies supporting these activities in general, and for structures in particular. There is a need for establishing appropriate target reliability levels for structures under temporary use taking into account specific circumstances such as reduced risk exposure times. This issue is being addressed in this article. Acceptance criteria for building-structure-related risks to persons obtained in prior studies are adapted to the special circumstances of nonpermanent risk exposure. Thereby, the general principle followed is to maintain the same risk levels per time unit as for permanently occupied buildings. The adaptation is based on the statistical annual fatality rate, a life safety risk metric that allows for a consistent comparison of risks across different societal activities and technologies. It is shown that the target reliability indices taking account of the temporary use of buildings might be significantly higher than the values suggested for permanently used structures.     

General Deterrence of Drunk Driving: Evaluation of Recent American Policies

A testable hypothesis of deterrence theory is that efforts to increase the expected cost of criminal activity by increasing the threat of punishment should, other things being equal, reduce the crime rate. In this paper, we examine whether the incidence of drinking and driving is responsive to escalation of the punitive threat. The recent national campaign against drunk driving provides a natural experiment in which to test the predictions of deterrence theory. Using state level data over the 1975-1986 period, we report no conclusive evidence that any specific form of punitive legislation is having a measurable effect on motor vehicle fatalities. We report suggestive evidence that multiple laws designed to increase the certainty of punishment (e.g., sobriety checkpoints and preliminary breath tests) have a synergistic deterrent effect. The most striking finding is that mandatory seat belt use laws and beer taxes may be more effective at reducing drunk driving fatalities than policies aimed at general deterrence.     

Review of Regulatory Emphasis on Transportation Safety in the United States, 2002–2009: Public versus Private Modes

The U.S. Department of Transportation is responsible for implementing new safety improvements and regulations with the goal of ensuring limited funds are distributed to where they can have the greatest impact on safety. In this work, we conduct a study of new regulations and other reactions (such as recalls) to fatal accidents in several different modes of transportation implemented from 2002 to 2009. We find that in the safest modes of commercial aviation and bus transport, the amount of spending on new regulations is high in relation to the number of fatalities compared to the regulatory attention received by less safe modes of general aviation and private automobiles. Additionally, we study two major fatal accident investigations from commercial aviation and two major automotive recalls associated with fatal accidents. We find differences in the cost per expected fatality prevented for these reactions, with the airline accident investigations being more cost effective. Overall, we observe trends in both the automotive and aviation sectors that suggest that public transportation receives more regulatory attention than private transport. We also observe that the types of safety remedies utilized, regulation versus investigation, have varying levels of effectiveness in different transport modes. We suggest that these differences are indicative of increased public demand for safety in modes where a third party may be held responsible, even for those not participating in the transportation. These findings have important implications for the transportation industry, policymakers, and for estimating the public demand for safety in new transport modes.     

Risk-Risk Balancing for Hazardous Waste Workers: Alternative Work, Traffic Fatalities, and Unemployment

Previous studies have shown that the fatality rate among hazardous waste remediation workers is likely to exceed the fatality rate averted among the public by remediation. The implication is that much hazardous waste remediation is inappropriate on a strictly risk-based basis. Such analyses ignore the fact that the same hazardous waste workers would be engaged in other work with similar or perhaps greater safety risks, and that in any case the single greatest cause of occupational fatalities is traffic accidents, hence distance traveled may be a more important predictor than type of work performed.     

Sense and Avoid Requirements for Unmanned Aircraft Systems Using a Target Level of Safety Approach

One of the most critical challenges to full integration of unmanned aircraft systems (UAS) into the National Airspace System (NAS) is the requirement to comply with CFR 14 Part 91.113 to “see and avoid” other aircraft. Various attempts have been made to develop systems to “sense and avoid” other aircraft so UAS can comply with the intent of the regulation. This article proposes a framework to develop effectiveness requirements for any SAA system by linking UAS characteristics and operating environments to midair collision risk quantified by a fatality rate. The framework consists of a target level of safety (TLS) approach using an event tree format. Safety has been identified as the most important consideration in the UAS integration process. While safety can be defined in many ways, the authors propose using a fatality rate metric that follows other statistics used in the industry. This metric allows for the use of a TLS approach to the development of SAA requirements for system certification. Failure to adequately link system requirements to safety could result in the implementation of SAA systems that either do not adequately mitigate the risk associated with UAS operations or are overdesigned, resulting in increased cost and complexity. This article demonstrates the use of the proposed framework to develop specific SAA effectiveness standards based on UAS weight and airspace class combinations.     

How Selective Are Real Wage Cuts? A Micro‐analysis Using Linked Employer–Employee Data

Using linked employer–employee panel data for Germany, we investigate whether firms implement real wage reductions in a selective manner. In line with insider–outsider and several strands of efficiency wage theory, we find strong evidence for selective wage cuts with high‐productivity workers being spared even when controlling for permanent differences in firms' wage policies. In contrast to some recent contributions stressing fairness considerations, we also find that wage cuts increase wage dispersion among peers rather than narrowing it. Notably, the same selectivity pattern shows up when restricting our analysis to firms covered by collective agreements or having a works council.     

Vehicle Emission Unit Risk Factors for Transportation Risk Assessments

When the transportation risk posed by shipments of hazardous chemical and radioactive materials is being assessed, it is necessary to evaluate the risks associated with both vehicle emissions and cargo-related risks. Diesel exhaust and fugitive dust emissions from vehicles transporting hazardous shipments lead to increased air pollution, which increases the risk of latent fatalities in the affected population along the transport route. The estimated risk from these vehicle-related sources can often be as large or larger than the estimated risk associated with the material being transported. In this paper, data from the U.S. Environmental Protection Agency's Motor Vehicle-Related Air Toxics Study are first used to develop latent cancer fatality estimates per kilometer of travel in rural and urban areas for all diesel truck classes. These unit risk factors are based on studies investigating the carcinogenic nature of diesel exhaust. With the same methodology, the current per-kilometer latent fatality risk factor used in transportation risk assessments for heavy diesel trucks in urban areas is revised and the analysis expanded to provide risk factors for rural areas and all diesel truck classes. These latter fatality estimates may include, but are not limited to, cancer fatalities and are based primarily on the most recent epidemiological data available on mortality rates associated with ambient air PM-10 concentrations.     

Prospect Theory and Limit Lines

Risk acceptance criteria in the form of limit lines are investigated in the context of prospect theory. This theory departs from utility theory in several respects, an important one being the use of weights other than probabilities in the evaluation of the expected impact of uncertain outcomes. Hypothetical functions reflecting certain attitudes toward consequences and rare events are developed and combined to produce several limit lines.     

Mandatory Belt Use and Driver Risk Taking

A study of driver behavior before and after a mandatory seat belt use law in Newfoundland found that the benefits of such legislation are not reduced by riskier driving, as has been suggested by some theorists. On average, belt use in Newfoundland increased from 16% of drivers before the law to 77% after the law. At the same time, the quality of driving changed very little when compared to control groups of Nova Scotia drivers, who were not subject to the law and whose belt use rates did not change. In only one situation did Newfoundland drivers differ from the control group in Nova Scotia: after the belt law, drivers in Newfoundland became relatively more cautious (slower) in their speeds on four-lane expressways. These data confirm the results of earlier less controlled studies that also found no changes in driving behavior following nonvoluntary changes in occupant protection. Since the "risk-compensation" hypothesis predicts such changes, it seems to have no merit in explaining changes in fatalities and injuries after occupant protection legislation.