Handbook of Human Factors in Litigation

Y. Ian Noy, Waldemar Karwowski, Y. Ian Noy, Waldemar Karwowski

• Publisher: CRC Press
• Year: 2004
• ISBN:
  9781134441662
• Edition: 1
• Topic: Law
• Subtopic: Criminal Law
• Index: Law

Using ergonomics in forensics can help prevent the recurrence of system failures through engineering or administrative controls. It can also raise the level of concern among professionals and the public regarding product, workplace, and service safety due to perceived exposure to liability. Often the litigation issues in liability cases boil down to human factors, ergonomics, and safety. The Handbook of Human Factors in Litigation provides a comprehensive reference that provides the tools necessary for the preparation, analysis, and presentation of forensic evidence. Compiled by experienced, internationally respected authors, this handbook represents the state-of-the-art in the application of ergonomics to forensic investigation. It contains information on the litigation process, forensic approaches and methods, important scientific data in the major application areas, and valuable case studies. It is a useful tool to help managers and designers deal with exposure to liability.

III
Driving Environments

13
Human Factors in Traffic Crashes

Rudolf G.Mortimer
Human Factors Engineering
Richard D.Blomberg
Dunlap and Associates, Inc.
Gerson J.Alexander
Positive Guidance Applications
Evelyn Vingilis University of Western Ontario

0–415–28870–3/05/$0.00+$1.50
© 2005 by CRC Press

13.1 Introduction to Human Factors Principles and Standards of Care

Traffic crashes are the most frequent cause of unintended fatal injuries in the U.S. when compared with accidents occurring in public places, in homes, or at work places (National Safety Council, 2001). They accounted for about 41,821 deaths and 3.2 million injuries that resulted from about 6.4 million crashes in 2000 (USDOT, 2001). Though these numbers are staggering and involve huge personal, emotional, and financial losses, the fatality rate per distance traveled has been steadily declining. If the fatality rate per vehicle kilometer in 2000 had remained the same as it was in 1970 at 2.9 fatalities per 100 million km, there would have been about 131,000 fatalities in 2000. Therefore, it is evident that highway safety has improved significantly over the years.

This trend has also been found in most other countries. The rates/distance traveled in Finland, Sweden, and the Netherlands are somewhat lower than in the U.S., while those in France and Israel, for example, are about 60% greater. Some countries, such as Morocco and Turkey, have rates about 20 and 10 times greater, respectively, than many European countries (National Safety Council, 2002). It has been estimated that road traffic crashes result in about 22 deaths per 100,000 population worldwide and are about 40% of unintended deaths.

Among the factors that have contributed to the reduction in fatalities are improvements in the protection afforded to occupants of cars and trucks, such as air bags, seat belt systems, child restraints and interior packaging; stepped-up enforcement and educational campaigns to reduce impaired driving, especially targeted against drinking drivers; restricted licenses for young drivers, etc. At the same time, other events have increased the toll of injuries and fatalities, such as the allowable duty time of truck drivers (which can lead to fatigue); elimination of helmet laws for motorcyclists in many states or requiring helmets to be worn only by the young; inadequate lighting and marking of bicycles and cyclists at night; proliferation of jogging as a health measure with its attendant hazards when joggers use the roadway or cross it (especially at night); the historical difficulty of seeing pedestrians in darkness; and continued problems of visibility and glare in night driving, among many others.

The vehicle, the environment, and the human all contribute variables that need to be considered in any analysis of traffic collisions. The emphasis in this chapter is on the human as a participant in the traffic system as a pedestrian, cyclist, or an operator of a vehicle, a perceiver of the environment, a decision maker, and a responder. The environment includes that within the vehicle and outside it. The vehicle and its relevant characteristics are those assimilated by the human so that the operator’s input and the vehicle’s output relationships have been learned. However, the vehicle also includes input-output relationships that are not well learned or understood by the operator, such as car drivers braking on a slippery road surface or maximum braking of motorcycles.

The highway-traffic-environment-human system is dynamic and complex. There are no simple solutions to increasing safety and no simple reasons for crashes. As Haddon (1970) pointed out, the system is multidimensional and requires an epidemiological approach to unearth the underlying causes of crashes. The human as driver, pedestrian, motorcyclist, cyclist, and other participant in the traffic system is at the center of it and has been assigned a large proportion of the causes of crashes, as the principal cause or as one cause in association with other parts of the system. In almost all cases, it would be inappropriate to allocate cause only to the human element, independently of the other components. It is important that those involved in forensic work have a systems orientation so that the performance of the human is considered in the context of the overall situation.

Forensic Data Gathering

Traffic collisions result from a failure in one or more parts of the traffic system. The forensic analysis starts with the collection of the basic factual data that may include a police report; an accident reconstruction; statements of witnesses and the actors directly involved; photographs or video pictures of the scene and vehicles; and a survey of the area drawn to scale. These data are usually supplemented by depositions of persons having some knowledge that may be of relevance. An examination of the location of the scene is useful or imperative to allow observations and measurements of distances, lighting, or sound features, assuming that the scene has not been significantly altered in the interim.

Based on such background information, the human factors investigator applies fundamental principles of psychology, physics, and other sciences to discern and evaluate the underlying failures that were causally related to the event and the means by which those failures may have been avoided. In evaluating the standards of care that may have been breached and that contributed to the event, it is not unusual for the human factors person to work with an accident reconstructionist or specialist in another discipline; thus, the combined effort results in a realistic appraisal of the contributing factors to the failure and the standards of care that should have been in place that could realistically, practically, and economically have been expected to be employed.

13.2 Objective and Scope

The subject matter of this chapter is extensive and books have treated various aspects of it. The chapter must be incomplete in some respects but will attempt to deal with some of the major areas of forensic human factors in the most common or lethal traffic collisions. The major topics of this chapter include human factors aspects of:

• Vehicles, such as marking and signaling systems and their role in rear-end crashes; headlighting for night-driving visibility and its effects on drivers’ visibility and night crashes; motorcycle braking systems and rider performance in crash avoidance; and railroad crossing safety factors in drivers’ information processing (Section 13.3, prepared by R.Mortimer)
• Pedestrian and bicyclist safety (Section 13.4, prepared by R.Blomberg)
• Highway signing and driver information systems (Section 13.5, prepared by G.Alexander)
• Effects of alcohol and drugs on traffic safety and human performance (Section 13.6, prepared by E.Vingilis)

13.3 Human Factors Engineering Affecting Visibility and Perception, and Performance of Drivers, Motorcyclists, and Other Road Users

Visibility in Night Driving

The rate of crashes at night is about four times that in daytime (National Safety Council, 2002). Although other factors are at play, such as a greater incidence of alcohol use in hours of darkness, reduced visibility must be a major factor in the elevated risk in night driving. One way this is demonstrated is by the expected 30% reduction in crashes that occurs when street lighting is installed where none was before (Rowan and Walton, 1976).

Drivers must rely on the illumination provided by headlights when other lighting is not provided. Motor vehicles are normally equipped with headlamps that provide a high beam and a low beam. The requirements for the performance of headlamps in the U.S. is set forth in Federal Motor Vehicle Safety Standard 108, “Lamps, Reflective Devices, and Associated Equipment,” which first became effective in 1968. The headlamp performance standard was essentially based on the Society of Automotive Engineers Standard J579a. The federal standard was amended in 1978 to adopt the revised SAE J579c Standard, which allowed a doubling of the total intensity of the high beam to 150,000 cd and an increase of 5000 cd (to 20,000 cd) in the maximum permitted intensity at the 0.5° down to 1.5° right seeing point. The change in the maximum intensity of the U.S. high beam brought it closer to the intensities permitted in Europe. The change in the low beam has meant an increase in direct glaring intensities from oncoming vehicles and indirectly by headlights of following vehicles reflected in rearview mirrors with some increase in visibility.

The High Beam

The high beam can only be appropriately used when there is no oncoming traffic and no traffic close ahead so as to avoid excessive glare to other drivers; it provides a wide swath of light with its greatest intensities aimed about parallel to the road surface. The intent is to provide visibility of the road at substantial distances ahead of the vehicle and to the sides of the traveled lane. Those goals can be readily achieved with high-intensity light sources.

The Low Beam

The low beam is designed to be used when meeting other traffic or when another vehicle is ahead and nearby. Low beams are now also used in urban areas in most countries with or without street lighting, although they have not been designed specifically to be used in that environment. The design of the low beam has been undergoing slow evolution over many years in order to try to compromise the need to maximize visibility while minimizing discomfort and disability glare.

In a situation in which two cars drive toward each other on a straight, unlighted, level road at night, with both using the low beam, the visibility of the drivers will gradually decrease as the cars come closer due to the glare from the opposing car’s headlamps. Recovery from glare in this case will occur before the cars meet because the glare effect is an inverse exponential function of the angle between the glare source and the driver’s direction of gaze. At large separation distances between the vehicles, that angle is small and the glare effect is potentially large because it is then mainly a function of the glare illumination at the driver’s eyes from the oncoming car. When the cars are approximately 100 m apart and drawing closer, the glare angle becomes much larger, reducing the glare effect so that the visibility can increase. The eye’s sensitivity is rapidly affected by glare or any bright source; when it is adapted to the usual mesopic levels found in night driving, the readaptation of the eye to lower levels of glare and illumination is relatively slow and can take a number of seconds. Up to 10 seconds may be needed for approximately full recovery from headlight glare (Mortimer and Becker, 1973).

Figure 13.1 shows an example of the visibility distance to a 12% reflectance object at the right edge of the road for car drivers at 30 mph approaching each other with low-and high-beam headlamps on a level, two-lane road. In this example, the visibility is a minimum at about 400 ft for the high beam meeting and at about 300 ft for the low beam before the cars meet and pass each other. Then recovery from the glare allows the visibility to increase. Figure 13.1 also shows that the curves cross when the cars are about 2400 ft (731 m) apart, indicating the separation distance when dimming from the high beam to the low beam should occur to best maintain visibility.

However, many variables affect this general process, such as the geometry of the highway; reflectivity of the pavement; lateral separation between the vehicles; location of the object to be detected (pedestrian, parked vehicle, bicyclist, sign, delineation stripe, etc.); reflective properties of the object; approaching vehicles; following vehicles; properties of interior and exterior mirrors; mounting location of headlamps and the properties and aim of their beams; street lighting; environmental conditions such as fog, rain, and snow; and driver variables such as age, workload, and attention.

FIGURE 13.1 Visibility of car drivers meeting on two-lane road with low and high beams.

Because of the many variables to consider that can affect the ability of a driver to detect and recognize an object, it is evident that no simple methodology can be reasonably applied to predict a driver’s visibility. In a human factors recreation of a collision, it is essential to know as many of the important variables as possible. Some of those will be detailed in the police report, photographs, and scaled diagrams of the scene. The paths traveled by vehicles, cyclists, or pedestrians may be determined from skid marks, postimpact trajectories, marks on the pavement, and other features normally provided in the accident reconstructionist’s report. The statements of witnesses may also provide useful information, although they are sometimes inconsistent with physical evidence and need to be treated with due respect.

Night Photography

Photographs taken at night will show limited information. Also, those photos will normally be taken with a flash device in order to show as much of the scene as the camera and film are capable of capturing. Retroreflective materials will be highlighted in such night photography. It is important to remember that the scene as shown in those photos will be different from what was visible to a driver who was relying on the illumination provided by headlamps. One important reason is that flash strobes have a much wider field of illumination and also are usually at greater intensities than headlamps.

Photographs are sometimes made in a recreation of the scene at night in an attempt to simulate the view available to a driver. Attempts to reproduce what was seen by a driver at night using photos, film, or digital media most often cannot do this fairly, even when an effort is made to use a control object with which to compare the scene, such as varying shades of gray that are part of the picture. The photos are then made at various exposures so that the gray that is just at threshold in the actual scene and in a photo is taken as an estimate of the apparent visibility of other objects of interest in the photo to replicate a driver’s view (Holohan et al., 1989). That process may have some limited value i...

Table of contents

• Cover Page
• Title Page
• Copyright Page
• Preface
• The Editors
• Contributors
• I. Professional Issues
• II. Human Performance In the Legal Context
• III. Driving Environments
• IV. Physical and Cognitive Factors
• V. Product Liability and Warnings
• VI. Human Factors Applications
• VII. Human Factors Terminology