Prediction in road safety studies: An empirical inquiry

Studies about the road safety effect of interventions are usually retrospective quasiexperiments. In these, one key task is to predict what would have been the safety of the treated group without the intervention. Such predictions can be made by several methods, one of which is to use a “comparison group.” We use 26 yearly counts of reported injury accidents for the Canadian provinces to examine which of several simple methods of prediction would have historically predicted best. We find that the use of more data does not always improve prediction. How well one predicts depends not only on the amount of data used but also on the extent to which the prediction method is in accord with the unknown time trend behind the accident counts. We also find that the use of a comparison group to predict is not always better than predicting that this year's count will be the same as last year's. In addition, the intuitive notion that a good comparison group is that which is thought similar to the treated group is too simple. Both similarity and size (as measured by the number of accidents) are important. Moreover, whatever preconceived notions of similarity we had, were contradicted by the data. If the history of accident counts on the treatment group and on several possible comparison groups is available, a simple method to select the most suitable comparison group is suggested.     

Multiple-vehicle traffic accidents in Hong Kong

‘Multiple-vehicle traffic accident’ refers to a crash between two or more moving objects. Unlike single-vehicle accidents, not all drivers involving in a multiple-vehicle accident are responsible for the occurrence of the event. Accordingly, variables such as road type, speed limit and number of vehicles involved in the accident are expected to play a much more important role in association with injury severity in multiple-vehicle accidents. To study the factors influencing injury severity of multiple-vehicle traffic accidents, a population-based study was conducted. The traffic accident data was obtained from the Traffic Accident Data System (TRADS), which was developed by the Transport Department, Police Force and Information Technology Services Department, Hong Kong. Multiple-vehicle traffic accidents (N = 10,630) occurring during the 2-year period 1999/2000 were considered. Potential risk factors such as district, human, vehicle, safety, environmental and site factors were examined. Categorizing injury severity into “fatal/serious” and “slight”, a stepwise logistic regression model was applied to the population data set. The district board, time of the accident, driver's gender, vehicle type, road type, speed limit and the number of vehicles involved are significant factors influencing the injury severity. Identification of risk factors for severe traffic accidents provides valuable information to help with new and improved road safety control measures.     

A macroscopic impact analysis of the safety efforts case study: Pedestrian fatalities

Any time there are reductions in accidents, advocates of any particular position are quick to claim that it is their “effect” that has improved safety performance. The work in this paper focuses on interpreting a traffic system's performance with respect to a specific type of accident by attributing a change in the number of accidents to the relative contribution of three effects: the activity effect, the safety content effect, and the structure effect. A method is developed and applied to the data sets of pedestrian fatalities that occured in Greece during the period of 1965–1989. The relative contribution of the effects as well as the pattern changes turn out to have a decisive influence. The possible uses and extensions of the method are also discussed.     

Looked-but-failed-to-see-errors in traffic

Danish studies of traffic accidents at priority intersections have shown a particular type of accidents. In these accidents a car driver supposed to give way has collided with a bicycle rider on the priority road. Often the involved car drivers have maintained that they did not see the bicycle until immediately before the collision even though the bicycle must have been clearly visible.

Similar types of accidents have been the subject of studies elsewhere. In literature they are labelled “looked-but-failed-to-see”, because it seems clear that in many cases the car drivers have actually been looking in the direction where the other parties were but have not seen (i.e. perceived the presence of) the other road user. This paper describes two studies approaching this problem.

One study is based on 10 self-reported near accidents. It does show that “looked-but-failed-to-see” events do occur, especially for well experienced drivers. The other study based on Gap Acceptance shows that the car driver acceptance of gaps towards cyclists depends on whether or not another car is present. Hypotheses for driver perception and for accident countermeasures are discussed.     

ARAMIS project: a comprehensive methodology for the identification of reference accident scenarios in process industries

In the frame of the Accidental Risk Assessment Methodology for Industries (ARAMIS) project, this paper aims at presenting the work carried out in the part of the project devoted to the definition of accident scenarios. This topic is a key-point in risk assessment and serves as basis for the whole risk quantification.

The first result of the work is the building of a methodology for the identification of major accident hazards (MIMAH), which is carried out with the development of generic fault and event trees based on a typology of equipment and substances. The term “major accidents” must be understood as the worst accidents likely to occur on the equipment, assuming that no safety systems are installed.

A second methodology, called methodology for the identification of reference accident scenarios (MIRAS) takes into account the influence of safety systems on both the frequencies and possible consequences of accidents. This methodology leads to identify more realistic accident scenarios. The reference accident scenarios are chosen with the help of a tool called “risk matrix”, crossing the frequency and the consequences of accidents.

This paper presents both methodologies and an application on an ethylene oxide storage.     

Inherent safety, ethics and human error

A patient is to have the damaged left kidney removed. To safeguard correctness of action several layers of expert checks have been performed prior to the operation, which results in the removal of the fully functional right kidney. Nobody asked the patient. The patient did not volunteer providing “unnecessary” information. The experts know everything …

An untidy house made out of flammable materials. A careless smoker left his lit cigarette unattended. A blow of wind and the house comes in flames. Would better construction materials have prevented the accident in spite of the carelessness of the inhabitant

A tricky medical condition which is expected to provoke a patient's fast health deterioration and their slow death. The doctor takes the initiative and responsibility of performing a risky operation. The patient's life is saved and their health is re-established.

This work is not, as initially intended, the result of a thorough investigation of accidents, neither contains a systematic collection of data that can support the conclusions or the suggestions made. It is in the main a compilation of personal views. These views have been established from the correlation of the results of numerous accident investigation reports with the causes of small and insignificant incidents. These incidents are related with the education of university students, regulations within an academic environment and from independent personal experience working in different countries and with people of different cultures. The analysis that follows, however, should not be perceived as a mere reference to university students and/or to a university environment. University is the place where the fundamental scientific and engineering principles are germinated while current and past university students are the future and current production and design engineers, respectively. The places where the presented incidents have occurred are not always relevant with the conclusions, thus they are not stated. The reason this article is presented here is that I believe that often, complex accidents, similarly to insignificant ones, often demonstrate an attitude which can be characterized as “inherently unsafe”. I take the view that the enormous human potential and the human ability to minimize accidents needs to become a focal point towards inherent safety. Restricting ourselves to human limitations and how we could “treat” or prevent humans from not making accidents needs to be re-addressed.

The purpose of this presentation is to highlight observations and provoke a discussion on how we could possibly improve the understanding of safety related issues. I do not intent to reject or criticize existing methodologies. (The entire presentation is strongly influenced by Trevor Kletz's work although our views are often different.)     

Attitudes of commercial motor vehicle drivers towards safety belts

Despite the fact that Hawaii has one of the highest seat belt use rates for passenger vehicles in the United States, and has had a mandatory seat belt use law since the 1980s, studies have shown that commercial motor vehicles (CMV) seat belt use rates are low. To better understand this phenomenon, a comprehensive survey of commercial vehicle drivers was conducted in Hawaii to ascertain attitudes and self-reported behaviors regarding seat belt use. A total of 791 drivers responded to a written questionnaire implemented at weigh stations and distributed to various trucking firms and transport centers. Approximately 67% reported that they use seat belts “always” when driving a CMV (commercial motor vehicle), yet when asked how often do other CMV drivers use seat belts, only 31% responded “always.” Interestingly, 86% of these same drivers reported that they use seat belts “always” when driving a personal vehicle. The major reason cited for non-use of belts was “frequent stops/inconvenience” (29%), and “not safety conscious” (23%). Notably, the self-reported use of safety belts is highest among operators of vans (88% said “always”), followed by buses (87% said “always”) and lowest among truck drivers (only 60% said “always”). In this paper, some of the differences between self-reported users and non-users are explored and a multivariate logit model was developed to predict the odds of belt use as a function of various factors.     

Quality assurance and staff training

“G.M.P. Trends” is an american magazine publishing extracts of inspection reports: It is an official statement of errors, faults, omissions observed in the US pharmaceutical industry as regard good manufacturing pratices. A comparison between the “G.M.P. Trends” and the (“BPF”) “Bonnes Pratiques de Fabrication” (Good manufacturing pratices) points out the errors, defects or omissions observed and thus enable t o remodel staff training (1) (2).

Staff training is dealt with different chapters of the “BPF” staff, documents, samples, computerisation and risk generating product. Staff training is regarded as a mean for action: objectives, priority aims, choices and exchanges are to be defined.

We intend t o develop an example of answer to staff training needed in the pharmaceutical industry. The aim of this answer is the implementation of the good manufacturing pratices in a system which guarantees quality. This training is carried out within the framework of the directives and recommandations of the W.H.O. and U.N.I.D.O. with as a target the manufacturing of tablets of essential drugs.     

A new analytical model about the relationship between nominal failure stresses and porosity for foamed metals under biaxial tension

Foamed metals have been widely used as various engineering materials, and their mechanical properties have also been drawing extensive attention. In the present paper, a new mechanical and analytical model is established for these materials with isotropic three-dimensional reticulated structure under biaxial tension, and the mathematical equation about biaxial nominal stresses is deduced for the biaxial tension at the beginning of failure of the porous body. With the relevant experiment, the relation formula is proved to be very effective. Different from the relevant theoretical system of Gibson and Ashby, the present mathematical relationship can be conveniently achieved from directly using the “beam theory” on this mechanical and analytical model. In addition, this relationship can be further expressed as the mathematical relationship among the nominal failure “deviatoric stress”, the nominal failure “average stress” and porosity, but the concepts of both the “deviatoric stress” and the “average stress” can appear just from the mathematical treatment.     

A preliminary evaluation of the impact of local accident information on the public perception of road safety

The World Health Organisation (WHO) estimate that road traffic accidents represent the third leading cause of “death and disease” worldwide. A number of countries have, therefore, launched safety campaigns that have reduced their fatalities. In almost every case, however, this reduction has not been matched by a fall in the total frequency of road traffic accidents. Low-severity incidents remain a significant problem. “Attribution error” provides one plausible explanation for this phenomenon. Most drivers believe that they are less likely to be involved in an accident than other motorists. Existing road safety campaigns do little to address this problem; they focus on national and regional statistics that often seem remote from the local experiences of road users. This paper, therefore, describes the design and development of a system to provide the general public with access to information on the location and circumstances of road accidents in a Scottish city. The closing sections describe the initial results from a psychometric study that is intended to determine whether the information provided by such an application will have any impact on individual risk perception.     

Mechanism of conductance switching: An optical investigation

Electronic conductance switching in devices based on thin films of an organic molecule has been studied. Switching between two conducting states has been induced by voltage pulse, while the states have been probed by optical and electrical measurements simultaneously. In situ optical measurements showed that electroreduction of molecules led to conductance switching and appearance of high-conducting state in the device. We could “write” or “erase” a state by applying electrical pulse and “read” it by measuring electronic absorbance and conductivity. The “write” and “read” processes have been carried out for many cycles to exhibit a correspondence between conductance switching and electrochromism.     

Commentary: Research Emphasis and Needs for the Environmental Field in the 1990s

The treatment, storage, disposal, and control of heavy metals to prevent their dispersal in the environment has seen increased attention over the last few years. There has been growing concern for the presence and contamination associated with heavy metals in both our water supplies and soils. Elements such as mercury (Hg) and cadmium (Cd) exhibit human toxicity at extremely low concentrations; elements such as silver, chromium, copper, zinc, and lead also exhibit toxic properties to humans, although the concentrations are orders of magnitude higher than those required for Cd or Hg toxicity. One of the most publicized cases of industrial heavy metal pollution involved the discharge of the catalyst methylated mercury chloride into Minamato Bay, Japan, from a plastic manufacturing factory. Microorganisms converted the sedimented compound to monomethyl-mercury, which led to an enrichment of this toxic metal in fish consumed by local people, some of whom succumbed to diseases caused by severe chronic mercury poisoning.

Similarly, concern has also increased over the past decade for the management, treatment, storage, and disposal of hazardous waste. This concern has arisen in part due to such events as the eruption of Mount St. Helens in Washington State (which demonstrated how “local” events can affect air quality hundreds of miles away), “acid rain,” the “greenhouse effect,” and accidents such as the Bhopal tragedy. Because hazardous waste can have such large affects on both human health and the environment, I have developed a list critical needs and research areas that should be addressed during the next decade to respond to these issues.     

On the prevention of accidents and injuries : A comparative analysis of conceptual frameworks

The meaning of prevention has changed as new applications of the concept have appeared. Ideas presented in eleven different conceptual frameworks are compared. Identification of the frameworks took place through searches in databases and relevant literature. Five are general by nature, while six relate to injuries and accidents. All are supported by just a few parameters, the time dimension being the most prominent. Compatibility was established on three additional dimensions: level (individual, organizational or societal); direction (“bottom-up” or “top-down”); and in relation to the trichotomy “host-agent-environment”. An attempt to synthesize all these dimensions into one general model of accident and injury prevention is presented.     

Research into the validity of the traffic conflicts technique

The use of near-misses and conflicts as an indirect measure of safety in widespread. The Traffic Conflicts Technique is one procedure for the indirect measurement of safety which has achieved a degree of formalization and attained a measure of popularity in many countries. However, doubts about the validity of the Traffic Conflicts Technique persist. In this paper we examine the conceptual foundations of indirect safety measurement when as data serve observation of events such as near-misses or conflicts. The key problem addressed is that of “validity.” A definition of what validity is to mean is suggested. The statistical machinery for the measurement of validity on the basis of empirical evidence is formulated and tested. With this, it may now be possible to move towards rational concensus about the potential of the Traffic Conflicts Technique and similar procedures for the indirect measurement of safety. As a by-product of the analytical results, a yardstick has been created by which to judge the relative performance of the many extant variants of the Traffic Conflicts Technique.     

Annealing Textures for Drawability: Influence of the Degree of Cold Rolling Reduction for Low-Carbon and Extra Low-Carbon Ferritic Steels

This work considers the optimization of deep drawing properties by studying the influence of hot rolling conditions, cold reduction rate, and final annealing on the evolution of steel sheet textures. Two steels have been selected: a low-C steel used for enameling applications, and an extra-low-C steel of the interstitial-free type. Results show that the intensity of {111} component—and, consequently, drawability—is considerably higher in the textures of cold-rolled and annealed sheets than in hot-rolled sheets. It is suggested that drawability of sheets annealed after cold rolling improves if greater than conventional reduction rates are used during rolling. Finally, it is shown that, contrary to what has sometimes been claimed, improvements of the “r” coefficient are not accompanied by a “pancake” morphology of the ferrite grains.     

An analysis of biorhythms and their influence on motor vehicle fatalities

The possible effect of proposed cyclic fluctuations of human sensitivity (28 days), intelligence (33 days), and physical (23 days) characteristics on motor vehicle accidents and fatalities was examined. Three methods of calculating these theoretical cycles were also examined. One method, the “Biomate” computer, was found to be unreliable in that it indicated 10.6% more days designated by the theory as critical than were actually present in a 300 case sample. In a sample of 141 motor vehicle fatalities (64 drug-free and 77 drug-associated) no correlation with the theoretical critical days was found for either group beyond that expected from random distribution. No evidence was found to support the increased likelihood of accident involvement on the “critical day” as implied by the concept of the “biorhythm” theory. Several possible sources of error in previously published reports are discussed.     

The single-filament-composite test: a new statistical theory for estimating the interfacial shear strength and Weibull parameters for fiber strength

For over two decades the single-filament-composite (SFC) test has been an important tool in the study of the failure of fibrous composites. The SFC test itself involves a single brittle fiber embedded along the center-line of a matrix specimen of both large cross-sectional area and strain to failure. With increasing strain, the fiber fractures progressively, breaking into an increasing number of shorter and shorter fragments. Surrounding each break a shielded or exclusion zone develops within which no further breaks typically occur. At some strain level ‘saturation’ occurs abruptly as the shielded zones finally occupy the whole fiber, thus leaving a final distribution of fiber fragments end-to-end. Two uses for the SFC test have emerged: one has been to estimate the interfacial shear stress, τ, in the exclusion zone, sometimes called the interfacial shear strength and usually idealized as a constant over this zone. The other has been to estimate the fiber strength distribution and in particular the Weibull shape and scale parameters, ρ and σ_l, for fiber strength appropriate to some characteristic ‘gage’ length, l, such as the mean fragmentation length. In the past, theoretical bases for these estimates have handled the statistics of shielding in ways that have led to quite large biases. The purpose of the present paper is to use some recent theoretical advances to develop more sophisticated estimation procedures for τ and the Weibull fiber strength parameters ‘ in situ’, and thus to eliminate various errors in previous methods. Straightforward computer programs (written in release 3 of Maple), which calculate the various quantities in the paper, will be provided by the first or second author on request.     

Simulation of wear in combustion engines

The presented model is based on the experimental findings about the importance of the nano-layers (10–70 nm) which are formed on the surface of both the piston ring and cylinder of combustion engines during production, running-in and the following use. This layer consists mostly of carbon coming from fuel, lubricant and graphite of the cast iron as well as of iron oxides. It is shown that the experimentally measured wear rate of about several nanometer per hour can be explained if we accept interpretation of wear as the “pressing out” of this nano-layer. In this paper, the rate of “pressing” out and the distribution of deformation across the layer have been simulated numerically and compared with a simple analytical model and experimental data obtained by measuring wear via radioactive isotopes.     

The effects of combining sanctions and rehabilitation for driving under the influence: An evaluation of the New Jersey alcohol countermeasures program

In contrast to many other state Driving under the Influence (DUI) programs developed in the United States in the 1970s as alternatives to traditional sanctions, the New Jersey Alcohol Countermeasures Program combined sanctions with mandatory education/rehabilitation for offenders. Three components were evaluated: DUI education, “treatment,” and Alcoholics Anonymous. For 2,734 first and repeat offenders participating in this program between 1979 and 1982, the program was effective in reducing DUI recidivism for program completers (66% while licensed and 51% while suspended) compared with noncompleters, but it was less effective in reducing subsequent moving violations while licensed (20% compared with noncompleters) and accidents while licensed (18% compared with noncompleters). Completers had higher rates of violations and accidents while suspended (9% compared with noncompleters). A small group of repeat offenders, missassigned to DUI education, had higher post conviction rates of negative driving events than those of comparable offenders assigned to “treatment” or Alcoholics Anonymous, indicating that for these offenders the latter interventions were more effective.