(The following is one in a series of cases I have investigated that illustrate the different forensic engineering methods I use to investigate the cause of failures and accidents that result in civil litigation.
The update is a very detailed, informative, easy to read – I think, description of the methods used to investigate the fatal motor vehicle accident (MVA). The description reads a little like a story which I think makes for an interesting blog on a forensic engineering investigation – we engineers are not well known as rapt story tellers.
A briefer version of this case was published earlier with a list of the methods I used. It’s a good case for illustrating how an engineering investigation sometimes unfolds, going, in a sense, from not knowing at the start about what to do to solve the problem to getting on with it, figuring it out, and solving it.
Original blog updated
The investigation of the fatal MVA is reported under the following main headings with several sub-headings:
- The case (a description of the fatal MVA, the legal/technical issues, and my client)
- Forensic engineering investigation of the failure and the methods used
- Preliminary findings of the investigation
- Post mortem (resolution and lessons learned)
Description of fatal motor vehicle accident (MVA)
The accident occurred a few years ago on a remote, snow-covered highway along the top of a seaside cliff in eastern Canada. A jeep-like vehicle travelling along the highway at dawn struck a pile of soil-like material left in the travel lane. The driver lost control of the vehicle and drove over the cliff and into the sea. The driver died in the accident. Passengers in the vehicle survived.
At issue, for purposes of the forensic engineering investigation, was the following:
- Whether or not the pile of material on the highway was a hazard
- If it was, determine the degree or severity of the hazard
- Also, whether or not the pile of material caused the accident
I was retained by the RCMP to investigate the accident and resolve the technical issues.
Forensic engineering investigation
The investigation was unique in that there were no guidelines or well developed methods in the engineering literature on how to investigate this type of accident and address the technical issues.
Fortunately, in researching the literature, I did find some very relevant scientific research on speed bump design that I was able to adapt to my problem with excellent results.
My forensic engineering investigation relied on the following methods. The methods are described below in detail. I believe the following listing of methods is quite informative by itself:
- Take briefing on the accident from the RCMP
- Review documents on the accident provided by the RCMP including police reports and survivor’s statements
- Travel to the area and visually examine the scene of the accident
- Generate a picture of the accident scene using Photoshop as it might have been seen by the driver moments before the accident
- Research engineering literature for methods on the investigation of obstructions on a highway
- Research scientific literature on speed bump research and design
- Research transportation authorities in North America and Europe
- Design a full scale preliminary re-enactment of the accident on bare roads
- Plan a full scale re-enactment of the accident on a snow-covered test site implementing refinements to the re-enactment including safety measures derived from the preliminary testing
- Design a videotaping and measuring of the re-enactment
- Construct a full scale test site on an airport taxiway
- Re-enact and videotape the accident on the test site
- Analyse the videotape for evidence respecting the technical issues
- Edit the videotape to portray the re-enactment in a report
- Report on the preliminary findings including safety issues
Description of forensic engineering investigative methods for a fatal MVA
1. Take briefing on the accident from the RCMP
The RCMP’s briefing described the accident scene, the accident, and their staff’s assessment of the speed the jeep was travelling at the time it struck the pile of material on the highway. The briefing was supported by photographs of the scene, the pile of material on the road, and the truck that deposited the material on the highway. Survivor’s statements on the accident taken by the police were included in the supporting documents. .
The RCMP wanted a forensic engineering investigation to determine what part, if any, the pile of material had in the fatal accident. Very specifically, investigate the technical issues as noted above.
2. Review documents on the accident provided by the RCMP including police reports and survivor’s statements
Reviewing existing documents and examining photographs is a standard first step in the forensic engineeing investigative process.
The police reports were quite valuable in describing:
- How the truck deposited the material on the highway,
- The dimensions of the pile – the width of a traffic lane long, several feet wide and several inches high,
- The range of speeds the vehicle was possibly travelling, and the most likely speed
- The time of the accident
- The snow-covered road conditions at the time, and
- The lighting conditions (dawn).
I read the survivor’s statements but these did not yield any data relevant to the technical issues.
While reading the documents and afterwards I sort of brain-stormed the situation and jotted down all and sundry that came to mind. It wasn’t long that I realized this was quite simply an obstacle on the highway. I figured there would be lots of information in the engineering and scientific literature on how to investigate different obstacles on and near highways and their effect on vehicle travel. I soon found out that I was wrong.
3. Travel to the area and visually examine the scene of the accident
This is also one of the standard, invaluable, initial steps in the engineering investigative process (see Ref. 1).
I drove to the scene of the accident and simply walked and looked at the part of the route travelled by the jeep. I was struck by the straight alignment of the highway and the uninterrupted line of sight for several hundred metres in the approach to the scene of the accident.
Why wasn’t the pile of material seen by the jeep’s driver well enough in advance to stop, even on snow-covered roads?
4. Generate a picture of the accident scene using Photoshop as it might have been seen by the driver moments before the accident
I took photographs of the highway while on site. There was snow on the ground in the area during my visit but not on the highway.
I had a photographer take one of the photographs and using Photoshop “colour in” the bare highway with “snow” to give it that snow-covered look existing at the time of the accident. The photographer also added a feature to represent the pile of material on the highway. The material was light in colour like snow or very light quartz sand.
The technique is called ”cloning” in photography when a small element of colour is taken from one part of a photograph and added to another. In this case many small elements of the white snow in my photograph were taken and placed on the bare highway to give it that snow-covered look. Additional elements were taken to build a feature that looked like the pile of material struck by the vehicle.
The touched-up photograph was very realistic in portraying the snow-covered road with the almost invisible pile of light coloured material in the driver’s lane. Invisible until just moments before the pile was struck by the jeep.
The pile of material was seen by the driver in those last moments as suggested by the angled tire tracks on the pile. The tracks indicated the driver braked and skidded sideways on the snow-covered road just before the pile was driven over.
5. Research engineering literature for methods on the investigation of obstructions on a highway
I had a technical library research the literature in North America and overseas for methods of investigating obstructions on highways and the effects of these on drivers. Nothing specific was found but we did come across a reference to research on speed bump design.
I had that Eureka..!! moment when I realized that a pile of material several inches high on a highway was a ”speed bump”.
6. Research scientific literature on speed bump research and design
I went back to the technical library and searched the literature on speed bump research and design in Canada, the U.S., England, and Australia. I struck gold. I found original research papers on work carried out in California. One paper was quite detailed in describing the precise layout of a test site. An objective of the research was the evaluation of the effects of different configurations and heights of speed bump on the control of vehicles travelling at different speeds.
This was precisely my situation: The effect of a speed-bump-like pile of material on the control of a vehicle on a highway. I had my forensic engineering investigative method.
7. Research transportation authorities in North America and Europe
I was asked to evaluate the severity of the pile of material as a hazard – if it was found to be such.
I went back to researching the scientific literature, particularly the various transportation authorities and agencies for information on assessing the severity of hazards on our highways. Groups like these set the standards for our highways. I found reference to “severity indexes”.
I did not pursue this research because, as you are certain to appreciate, I was starting other tasks in the engineering investigation, particularly planning, design and construction of a “speed bump” test site.
As you will see in the following, I did not need a severity index classification system to tell the RCMP that the pile of material involved in the accident was a hazard and a severe one.
8. Design a full scale preliminary re-enactment of the accident on bare roads
I decided to carry out a full scale re-enactment of the accident, initially on bare roads in the interests of safety. I wanted to learn how the vehicle would behave on bare roads and use the data to refine the design before planning to carry out similar tests on more dangerous snow-covered roads.
A full scale field test that simulates conditions during an accident – a re-enactment, is simple, practical, visual, and the results are easy to understand/see by non-technical people.
My design consisted of a simple modification of the speed bump research sites that I found in the literature. The modification included the dimensions of the pile of material and the highway lane width at the accident site. It was a fairly simple design to think through and portray in a drawing to guide construction.
The design consisted of the lane of a “highway” with the pile of material and its dimensions shown on the drawing part way along the lane.
The area of the lane beyond the down-highway end of the pile of material was marked off in one foot graduations across the lane. Like a large ruler on the lane.
Similar graduations were marked off on a large sheet of plywood but at six inch intervals. This was to form a vertical ruler set off to the side of the lane opposite the pile of material.
The test lane was about 400 feet long with the pile of material near the middle. The lane was made the same width as at the accident site. The pile was cone-shaped in section along the lane. It extended across the lane and about 10 feet along the lane. The pile was about 15 inches high.
The re-enactment would involve driving the jeep-like vehicle down the lane at different speeds and over the pile of material. It was expected the jeep would be airborne after hitting the pile of material, as found during the speed bump research. The rulers would measure how high and how far the jeep travelled airborne before landing back on the lane. It was expected that the height and distance would vary depending on the speed.
9. Plan a full scale re-enactment of the accident on a snow covered test site implementing refinements to the re-enactment including safety measures derived from the preliminary testing
This was the plan – taking full scale testing in stages – first on a bare road then on a snow-covered road, and learning as we progressed. But testing wasn’t carried out on a snow-covered site for a very good reason as explained below.
10. Design a videotaping and measuring of the re-enactment
It was decided to film the field tests to get a record of the jeep’s behaviour as it drove down the test lane and over the pile of material. The filming would also record the measured height and distance the vehicle would be airborne during the test.
A camerman would be stationed opposite the pile of material to record the height and the distance the jeep travelled airborne. Another was to be positioned in the bucket of a boom truck down the lane and approximately 50 feet above the lane to film a birds-eye view of the travel of the vehicle as it drove over the pile of material and on down the lane. A third was to ride in the jeep with the driver to record the behaviour of the vehicle as experienced by the driver.
Finally, a camerman was to fly over the test site in a helicopter to record the layout of the test site. The camerman would also film the vehicle stationary on the pile of material at the angle suggested by the tracks in the pile at the accident site. The RCMP provided the helicopter.
11. Construct a full scale test site on an airport taxiway
A full scale test site was constructed on an airport taxiway according to the design and dimensions described above. Permission to use the taxiway was arranged by the RCMP.
12. Re-enact and videotape the accident on the test site
Tests were carried out and filmed driving the vehicle over the pile of material at speeds of 20 km/hr initially and then at 30 km/hr. The jeep was driven across the pile at right angles instead of at an angle as thought to have occurred during the accident.
Tests were planned at higher speeds including the 50 km/hr travelled by the vehicle during the accident as concluded by the RCMP. These tests were postponed because they would have been too dangerous without safety provisions for the driver.
I drove the vehicle during the tests. I was struck by the erratic behaviour of the jeep on driving over the pile of material at 30 km/hr and the measure of difficulty controlling the jeep to avoid hitting the boom truck down lane.
13. Analyse the videotape for evidence respecting the technical issues
It was enough experiencing the erratic and dangerous behaviour of the jeep during the test at 30 km/hr on bare highway, and viewing this on film, to conclude that the pile of material was a hazard on a snow-covered highway at 50 km/hr. This resolved Technical issue #1 above.
There was insufficient information to assess the severity of the risk except to suspect it was high by whatever standard of evaluation was used. Technical issue #2.
There was insufficient information to conclude if the pile of material caused the fatal MVA. Technical issue #3.
14. Edit the videotape to portray the re-enactment in a report
There was approximately 30 minutes of film recorded by the three cameramen during the testing in this case. This was edited to approximately 4 minutes for each camera and transferred to a DVD with voice overlay describing what was being viewed in each of three windows. The DVD accompanied a report on the testing.
15. Report on the preliminary findings including safety issues
A report was prepared on the testing generally as outlined above. The report basically concluded that it was too dangerous to continue the testing without safety precaustions for the driver.
The report was presented to the RCMP and reviewed in a meeting. The RCMP stopped the testing all together stating, “You’ve told us all we need to know”. Presumably, the testing addressed all the technical issues to the satisfaction of the client.
The RCMP indicated, by stopping the forensic engineering investigation at the conclusion of an abbreviated preliminary stage, that the technical issues had been resolved and that they knew the cause of the fatal MVA.
The matter was settled out of court.
1. The importance of researching the scientific and engineering literature. It’s easy today and there’s lots out there.
2. Full scale field tests are practical, and the results are easy to see and understand by non-technical people.
3. Professional cameramen should be retained to film all field testing, particularly cases where movement is involved.
4. The value of generating a picture of the scene of an accident or an engineering failure at the time of the incident using programs like Photoshop.
1. “Technical” visual site assessments: Valuable, low cost, forensic engineering method. My blog posted on this site, September 4, 2012