Road Management & Engineering Journal
September 1, 1998
(U.S. and Canada)
Fax: (360) 335-6402
Crash reconstructionists, road safety educators, police and traffic engineers should work together to identify the circumstances that lead to crashes.
By Dan Keegan
|An edited version of this article was published in the Globe and Mail (Canada's national newspaper) on November 21, 1994, following a conference of crash investigators and reconstructionists in Toronto.|
A few years ago, on a bright November morning, a pickup truck ploughed into a group of 13 cyclists on a highway near London, Ontario. One of the cyclists, Greg Curnoe, a popular local artist, was killed. Several others were injured.
It was a flat two-lane road. The cyclists were colourfully dressed. The pickup driver, it was determined, was not impaired by alcohol or drugs. It seemed an inexcusable breakdown in driving performance. The pickup driver said he simply didn't see the cyclists, and this, for many, was difficult to accept. Many people were angered when the driver walked free from a charge of dangerous driving, a criminal offence with a maximum 14-year jail penalty. The court felt that the criminal charge was too severe. A lesser charge of careless driving wasn't brought because it didn't seem severe enough.
What could possibly explain crashing full tilt into something so obvious as 13 brightly dressed cyclists? For the average police officer called to investigate such an accident it might be hard to think of anything other than a criminal charge, but for a specialist in Human Factors (the science of studying how humans perform tasks) there are all kinds of possibilities. These possibilities were the theme of the 10th annual conference of the Canadian Association of Traffic Accident Investigators and Reconstructionists (CATAIR) held in Bramption, near Toronto, recently.
Accident investigators listened and watched as some of North America's top experts on how humans perform the task of driving an automobile explained their trade. For example, they saw U.S. accident investigator Bill Fischer explain how he reached 25 years back into the past to reconstruct the infamous incident at the Chappaquiddick bridge that took the life of Mary Jo Kopecne and ended Ted Kennedy's hopes for the U.S. presidency.
Fischer's analysis was featured in a BBC TV documentary recently. At the outcome, he had Mary Jo Kopecne alone and driving the doomed car as it approached the bridge. Using the modern tools of his profession, he started with Kopecne's car upsidedown in the water, calculated backwards from the damage to the car, the tides and level of the water, the skid marks on the bridge, the capability of the brakes, the nature of the approach road, and estimated Mary Jo's speed at about 33 mph. It was very dark and she wasn't familiar with the road. The bridge was at an angle to the approach road and it was low and not very visible in the headlights. At that speed, with a blood alcohol content of 0.09% slowing her reactions, Kopecne wouldn't have had a chance, says Fischer.
Fischer's conclusion that Kennedy was not the driver, and in fact wasn't in the car at all, was based on the peculiarities of Kennedy's story and Fischer's knowledge of human factors. Would Kennedy, with his familiarity of the area and his driving experience, have missed the bridge in the first place? It seemed more likely that Mary Jo Kopecne would. Could Kennedy have exited the car, in the dark, upside down, and with a high blood alcohol level? Based on his knowledge of human capabilities in similarly stressful situations, Fischer thought not.
The common thread -- a deceptive violence
The two crashes described above were different in fundamental ways but there was a common thread -- the everyday world of driving is deceptive. Beneath the surface of the familiar and the commonplace, is a treacherous world of hidden dangers. Most notable is the inherent power and potential for violence that is concealed from our senses by the technology of the modern automobile. The late professor Marshall McLuhan, renowned guru of the technological age, once observed that "all the rhinos and hippos and elephants in the world, if gathered together in one city, could not begin to create the menace and explosive intensity of the hourly and daily experience of modern city traffic."
But drivers, lulled by the uneventfulness of the typical traffic stream, and cocooned in the comfort of their vehicles, tend to be oblivious to this powerful undercurrent of violence, until a miscalculation or an unfortunate combination of circumstances brings it ripping to the surface. Suddenly, the routine trip to the store, the daily delivery, the trip with the family, can turn into a sort of twilight zone of disbelief, where complacency is shattered and the consequences can be a nightmare.
How it happens
The first instinct when investigating accidents such as the one that killed Curnoe, is to look for some dramatic impairment in the driver such as alcohol or drugs. If this isn't found, then the search shifts to the driving environment, for some anomaly that might have fooled the driver or caused vehicles to go out of control. In both of these areas, the science of Human Factors has much to offer.
Most critical in understanding the problem of accidents is understanding that drivers don't necessarily see things just because they're there and clearly visible. Their eyes, which collect 90% of the information used in driving decisions, have to gather information rapidly. They can't see everything that's there so they do their job selectively, flicking about from the road ahead to traffic, the mirrors, and anything else that catches the driver's interest. Experience plays a critical role in where drivers look and what they see. In the world of human factors, that's called "expectancy."
Expectations the key factor
"Driver expectancy is a key factor in driving task performance," human factors specialist Gerson Alexander told crash investigators at the conference. If drivers can easily get the information they need and know what to expect, they can manage themselves in traffic more effectively. And traffic engineers try to oblige. As head of the human factors program for the U.S. Federal Highway Administration, Alexander developed the concepts of Driver Expectancy and Positive Guidance that play an important role in the design of today's highways.
But while engineers have made great gains in providing guidance cues for drivers there are still many problems. The down side of making roads and traffic more predictable is the complacency this can engender in drivers. Drivers gather much of their information subconsciously. In a non-threatening environment inattention becomes the threat, and it can lead to disaster, particularly when a driver is impaired. The impairment doesn't have to be alcohol or drugs. Fatigue, distractions, or anything else that affects the ability to efficiently divide attention, select information, and make decisions, can cause problems. In the Curnoe case, some of the cyclists recall a striking visual effect in a nearby field as a barn appeared to be floating in flood waters from the Thames river. This could be a powerful draw on the attention of a driver who has missed seeing hazards on the roadway.
The "expectancy violation"
Another dimension to this dilemma is what Alexander calls the "expectancy violation." An expectancy violation is a situation in which drivers are, in effect, set up by their own expectations of traffic and roadway and then become very susceptible to false cues. A classic example, and one that many drivers will likely recognize, is where a highway curves, but a sideroad (perhaps unpaved) cuts off at a tangent. The driver approaching the curve at night, especially one unfamiliar with the road, may look ahead and mistake the sideroad for a straight highway. The power of this illusion is greatly enhanced if some of the stronger highway cues (telephone poles, for example) suddenly depart from the main highway and follow the sideroad as well. Deceptive treelines that follow the sideroad can create the same kind of illusion.
Alexander recommends procedures for highway engineers to follow in determining driver expectations and providing positive cues to guide them. To identify violations of expectancy he recommends, among other techniques, that engineers talk with maintenance personnel, police, operational personnel, and have drivers who are unfamiliar with the road do a drive-through.
There are so many things that can go wrong for the unwary driver that, looking from another point of view, it's amazing that there aren't many more accidents. The driving environment is a jungle, with a huge variety of traps for the unwary. And drivers, for the most part, are both oblivious to the traps and naive about their own limitations in dealing with them. The result? Over the next year between 3,000 and 4,000 Canadians will die on our roads. Many thousands more will be injured and the total cost to society will amount to many billions of dollars.
How crash investigators can help
Every time one of these crashes occurs, investigators will have a chance to go beyond merely assigning blame and to learn a bit more about the traps and the abilities of humans in dealing with them. Can this information be useful in preventing crashes in the future? Constable Mick Logan, an accident investigator attending the CATAIR conference from the U.K., feels it can.
"The highway engineer intends information to get to the driver," Logan says, "and he thinks he's done it. But the driver may not be seeing what the engineer thinks. In investigating an accident you see the problem, either in driver behaviour or the driver not appreciating what the highway engineers are trying to do. We ought to be a catalyst to bring them together. There may be a role for the investigator in educating drivers and engineers."
This kind of communication between different stakeholders in the ongoing war against traffic casualties is difficult to organize but it's importance has been recognized. In fact it was one of the concerns that emerged from a recent workshop on road safety held by the Canadian Council of Motor Transport Administrators (CCMTA). The CCMTA is already working on a communication infrastructure that could make it easier for crash investigators to help engineers peer into the future and perhaps predict where and when the deadly mix of environmental traps and human limitations might find their next fatal combination.
Footnote: Highway 407, a brand-new hi-tech motorway just north of Toronto that collects tolls electronically, was scheduled to open at the end of 1996. However, on the advice of police, the opening was delayed while serious design problems were corrected. Police saw dangers such as unprotected bridge abutments and lack of a median barrier, that were not considered to be safety flaws by the design engineers. The highway opened in mid 1997 following the expenditure of millions of additional dollars to correct the flaws. Subscribers can read more on this in the Vol 7, No 2 issue of the [PDE Publications'] Driver/Education newsletter (What's happening -- Role in highway design for educators, police).