Risk Homeostasis Theory and Traffic Accident Data

The risk homeostasis theory posits, in essence, that a control mechanism analogous to the thermal homeostatic system in warm-blooded animals tends to keep risk per unit time constant, and, as a consequence, the number of traffic accidents per unit time of driving also tends to remain constant, essentially independent of changes in the traffic safety system. It is the purpose of the present research to examine the validity of this claim using a wide variety of traffic accident data. All the data examined are found to be incompatible with the risk homeostasis theory. The only specific field accident data offered in the literature to support the risk homeostasis theory are found to, in fact, refute the theory. The accident data provide evidence that a rich variety of user responses occur. While it is possible for users to collectively respond in such a way that safety benefits are completely cancelled, such a response is not particularly common; it is certainly not universally occurring, as suggested by the risk homeostasis theory. It is concluded that the risk homeostasis theory should be rejected because there is no convincing evidence supporting it and much evidence refuting it.     

Artificial intelligence and formal models of international behavior

During the past five years, models and techniques developed in artificial intelligence (AI) have been applied to a wide variety of topics in international relations (IR). These applications build on a theoretical base established at MIT during the 1970s, and the expansion of the applications reflects both changes in AI research and limitations of alternative models such as statistical modeling and rational choice approaches. Current applications in IR/AI tend to fall into three categories. First, there have been extensive applications of if-then rules in expert systems and simulations. Second, many models emphasize the role of historical precedent in IR decision making. Third, a variety of approaches employing natural language are under development. These AI techniques have extended considerably the range and complexity of formal models of international behavior. He has spent the past four years working on applications of artificial intelligence to the problem of making short-term predictions of international behavior. He is author ofMicrocomputer Methods for Social Scientists (Sage 1987) and numerous articles on mathematical modeling.     

Estimating Fatality Reductions from Increased Safety Belt Use

Fatality reductions from increases in safety belt use are estimated taking into account that drivers who change from being nonusers to being users have lower accident involvement rates than the remaining nonusers, a process referred to as "selective recruitment." Analytical functions are derived which express expected fatality reductions in terms of changes in safety belt use rates from an initial rate. The function parameters are determined by requiring that computed average crash rates for nonusers be 53% higher than the rates for users, a recently determined empirical value. These functions show that, depending on the initial use rate and use rate increase, selective recruitment may increase or decrease expected fatality reductions. However, effects are relatively small, in no case exceeding +/- 5.3%.     

Factors influencing middle and high schools' active parental consent return rates

The authors examined factors influencing the return rates for attempting to collect active parental consent forms from 21,123 students in the 7th through 10th grades in 41 middle and high schools. Overall return rates from middle schools were higher than from high schools. Schools that offered high levels of staff support for collecting consent forms had higher return rates. Procedures where the consent form was attached to a school form that parents had to complete and return to the school yielded the highest return rate. Implications for how researchers can obtain a high parent consent form return rate are discussed.     

Nonverbal cues employed in discriminating between disabled persons and actors

Undergraduate subjects were seen to accurately discriminate between simulating actors and genuinely disabled males confined to wheelchairs. Judgments were based on skill in manipulating the wheelchair, poorer muscular development of the disabled, and on appearance of clothing. Implications for research on the disabled employing actors was discussed.This study was supported by a grant from the York University Faculty of Arts awarded to the first two authors. The project was performed as the third author's Honours thesis. The authors wish to thank all participants for their cooperation and assistance in making this research possible. The authors also wish to thank Gail Kenyon, Coordinator of the Centre for Handicapped Students who helped recruit participants for the videotaping and to Lucie Cantrell, Executive Officer of the York University Counselling and Development Centre who arranged for the use of the Centre's facilities and equipment.     

On trends and constants in periodic autoregressions

Periodic autoregressions are characterised by autoregressive structures that vary with the season. If a time series is periodically integrated, one needs a seasonally varying differencing filter to remove the stochastic trend. When the periodic regression model contains constants and trends with unrestricted parameters, the data can show diverging seasonal deterministic trends. In this paper we derive explicit expressions for parameter restrictions that result in common deterministic trends under periodic trend stationarity and periodic integration.