Pages: 7

A young man on a motorcycle in a dark, rural area ploughs into a moving train at a railway crossing at night. He passes between two black rail cars, losing both his arms and one leg in the process. Miraculously, he survives. The only warning of the crossing was a sign. There were no flashers or gates. A second crash involves a nurse on her way to work. She enters an intersection just as her light turns green. She strikes a teenager crossing at a red light. The nurse's view towards the pedestrian is blocked by an SUV in the left turn lane. A third crash occurs when an older man (directed by his teenage grandson) looks for the entrance to a crowded shopping centre and rear-ends the vehicle ahead when it slows suddenly. The physical, visual, and mental limitations found in all road users can result in crashes, even when the driver or pedestrian is attentive, alert, and conscientious. Investigating the How and Why of Motor Vehicle Crashes: To Err Is Human describes some of the remarkable stories and fascinating science associated with a selection of the 500 crashes the author has investigated. The author's work as a human factors specialist draws on knowledge from psychology, physiology, kinesiology, and engineering design. The aim is to reduce errors, injuries, and deaths. An introductory chapter is followed by 10 chapters, each dealing with a particular crash. Each chapter begins with a description of the collision, the investigation, the human factors issues, the underlying science, the analysis, the conclusions, and the countermeasures that would prevent similar crashes, and in some cases, court findings. The final chapter describes some of the court process for a human factors expert, as well as experiences the author has had, both pleasant and unpleasant, in court. The intended audience for this book includes police, lawyers, insurers, investigators, engineering and psychological forensic specialists and technical students in related fields, and anyone who has been in or witnessed a crash.

Pages: 13

This chapter describes an accident in which a driver encountered a pedestrian lying on the roadway in a poorly lit area at night. The driver was unable to stop in time and struck the pedestrian. For reasons that will be explained, he did not know he had hit someone until he returned to the scene a few hours later. Issues discussed in The Science section focus first on how far away it is possible to see low contrast targets such as pedestrians in dark clothing with low beam headlights. The second critical issue is that of expectation, that is, whether the driver is expecting to encounter a target or not. With respect to the investigation, the original site of the collision had been modified, and could not be used for a re-enactment. The criteria and challenges of finding an acceptable similar location are described. Besides location, the re-enactment had to be carried out at a time of day and time of the year when the light level and the traffic volume were equivalent to that at the time of the collision. These considerations are discussed.

Pages: 14

This chapter describes a collision that resulted when an inattentive driver ran a red light at an intersection. His vehicle was struck by another vehicle when its driver crossed the intersection on a green light. The main human factors issues explored deal with the design of the eye, central (foveal) vision, peripheral vision, visual search (bottom-up versus top-down), the useful field of view of the eye, and the length of typical eye fixations. All these issues affect the ability of a crossing driver who has a green light to detect a red‐light runner in time to do anything about it. Solutions which can improve signalised intersection safety are discussed. The trial outcome is briefly described.

Pages: 11

This chapter describes a collision involving a motorcyclist and a train at a crossing in a rural area at night. As the motorcyclist drove towards it, he failed to see a train in the crossing until it was too late to stop. He passed between two black oil tanker cars and ended up on the other side of the train. He survived, albeit with serious injuries. This rail crossing was the most basic of crossings. When a train approached, there were no gates that come down to force drivers to stop and there was no real-time warning by means of flashing lights or bells. There was just a simple railway crossing sign to warn drivers that there was a railway crossing at this location. The main human factors issues discussed in The Science section are the visibility of a train at night, and the limitations of warning signs at train crossings. Solutions to better warn drivers of the presence of a train at night are described. The motorcyclist sued the railway for not providing sufficient visibility of the train. The case went to trial. The judge's findings are discussed.

Pages: 15

This chapter deals with a case involving a rear-end crash where eyewitness evidence was crucial. Two vehicles were following one another when the first one slowed to make a left turn into a commercial driveway. The left-turning driver claimed he was stopped, for several seconds, waiting to turn, when he was suddenly struck from behind by another vehicle. The following driver said, on the contrary, the driver in front was not stopped but had slammed on the brakes at the last moment, resulting in a collision. The question at issue is how two people who witness an event can come up with such different stories. The answer has to do with the first issue (information processing, memory, and biases) considered in The Science section, which is our ability to take in or “process” information and remember it accurately. The many ways in which witnesses’ memories can be biased are reviewed. The second Science issue considered is the time and distance that need to be maintained between two vehicles, one behind the other, to ensure that the following driver can stop in time should the driver in front have to stop quickly. This depends, in part, on the following driver's perception-reaction time. It also depends, among other things, on the state of the brakes and the friction between the tires and the road surface.

Pages: 16

A large percentage of crashes at intersections are associated with view obstructions. This chapter describes such a collision involving a pedestrian, potentially distracted by her cell phone, who stepped into an intersection just before her light turned red. She was struck by a driver on the cross street, who had entered the intersection just after, as the driver's red traffic light turned green. The driver's view of the pedestrian was partially blocked by an SUV stopped in the adjacent left-turn lane. The human factors issues explored in The Science section deal with the effect of high workload on the driver's likelihood of detecting a pedestrian in a timely fashion. This is especially true when the pedestrian is seen in peripheral vision or more than 10° off the line of sight. The effect of cell phone use on teenage behaviour while crossing intersections is described.

Pages: 15

While driving on a highway at night, a tractor-trailer driver suddenly encountered a disabled car with no lights, protruding into his lane. He did not see it in time to swerve or to brake. He struck the vehicle, resulting in injury to its two occupants. The human factors issues explored in this chapter deal with the visibility cues that were available to the truck driver and how far away a driver with normal vision would be expected to see the disabled vehicle by means of those cues. Also explored in this chapter is how the human factors expert and the engineer who does the collision reconstruction work together to understand how the collision came about. The limitations of video for assessing visibility are discussed. This chapter also explains the very large impact on seeing distance of expectation, that is, knowing that a hazard lies ahead.

Pages: 15

This chapter describes a collision at a railway crossing in which a bus driver drove into the side of a train, resulting in multiple injuries and deaths. The flashers had been on and the gates were down at the crossing for over 20 seconds before the collision. This chapter deals with one of many possible causes of this crash, namely driver fatigue. The science concerning fatigue was reviewed to determine if it could have been a factor for the bus driver. Whether or not “fatigue” is present is not a simple question that can be checked off by a police officer on a motor vehicle collision report. The Science section of this chapter deals with what is meant by “fatigue”, as well as the many factors which can lead to fatigue's effects, including lowered alertness and poor performance. Solutions/countermeasures to fatigue are discussed. After a review of The science, fatigue did not appear to be a factor in this collision. The author's work on fatigue was part of a larger investigation by the Transportation Safety Board of Canada (TSB) — an independent agency that investigates air, rail, marine, and pipeline occurrences (and selected roadway crashes when they involve one of the other modes of transportation). The likely causes of the collision according to the TSB are discussed.

Pages: 9

This chapter describes a night-time crash involving a driver of a passenger vehicle in a rural area who encountered what she thought was an oncoming vehicle with one headlight moving into her lane. She began pulling over to the right to avoid it. After 10 seconds she rear-ended the mystery vehicle. It was a tractor with a white work light facing rearward and a “SLOW-MOVING VEHICLE” sign on the back. The scientific issues important in this case were expectancy and pattern recognition in relation to the automatic dipping of high beam headlights in response to oncoming headlights, and the confusing single white light, which appeared to be oncoming in the driver's lane. Driver difficulties with the perception of closing speed added to the difficulty for the driver in understanding what was happening. The effect of glare from the work light next to it made the “SLOW-MOVING VEHICLE” sign virtually impossible to see.

Pages: 12

A young man was driving two friends to their homes late one rainy night. He entered a work zone and was confused when the road split into two sections, one curved and one straight. The straight portion was the continuation of the old highway. The curved portion was the newly reconstructed road. Too late, he realized he needed to take the curved roadway. According to police, he was going too fast when he entered the curve. He left the road and struck a large rock. The driver and both of his passengers were killed. This chapter considers mental (information processing) workload for drivers in a work zone, how driver expectations affect response, seeing distance available to lane markings in the rain at night, preview distance required to follow the road path comfortably, and PRT. Also discussed is the importance of seeing the crash site under the same conditions (lighting, weather, road layout, and traffic control devices) that were present at the time of the crash.

Pages: 13

A driver intending to turn left at an urban intersection struck a bicyclist ahead of him who was stopped on the left side of the lane, in the centre of the roadway, also intending to turn left at that intersection. The collision occurred in darkness with overhead streetlights partially illuminating the area. The road surface was wet from rainfall earlier in the day. The bicyclist was wearing a jacket with retro-reflective stripes and reflective ankle straps. He may have been equipped with a flashing red light. As the driver approached the intersection, his attention was drawn to a vehicle pulled over at the curb to his right, and to a pedestrian who was partially blocked from his view by the pulled-over vehicle. The pedestrian appeared to be about to cross at the intersection crosswalk. The driver who struck the bicyclist was looking to his right to see if the pedestrian was on the crosswalk or not, and in so doing failed to detect the waiting bicyclist to his left. The Science section of this chapter deals with issues of driver visual search, visibility and conspicuity, visibility and rain, glare and streetlighting, and driver distraction. This chapter also deals with concerns when collecting speed measurements. A countermeasure considered is the value of an overhead flashing light at the crossing that could be triggered by a pedestrian wishing to cross.

Pages: 16

This chapter gives the reader some insight into work as a human factors expert witness. It begins with how one finds work in this area, and then describes the various stages involved in a legal case, including the initial contact, the site visit, a verbal opinion, and the writing of a report (if one is desired). Only about 5% of cases go to court, most likely because of the expense and time involved. When the case goes to court, there is a lengthy preparation, sometimes involving role playing with the lawyer beforehand. In court, there is a process of qualification as an expert in court. Both lawyers and the judge must accept you as an expert to be qualified. This is important because once qualified, experts are allowed to give “opinion” evidence which can only be rejected on the basis of evidence from another expert in the same area. Once qualified, the expert goes through their report, usually structured as a series of questions and answers between the lawyer and oneself, in the examination-in-chief. This is followed by the often gruelling cross-examination. The re-direct allows your lawyer to clarify any issues raised in the cross-examination. Where available, the judge's findings are reported. Throughout, illustrations from the author's own experiences and expertise as an expert witness in human factors are used.