How fast was he driving when he hit the girl on the sidewalk?  He’s dead now after falling asleep at the wheel, hitting the girl then hitting a pole.  So’s the girl after sliding several metres in the grass.  Speed is important in reconstructing an accident like this.

His speed can be assessed from the damage to his car.  It’s called a “crush” analysis, not surprisingly.  The assessment can be cross-checked with a different analysis using data from the skid marks of the girl in the grass.

Experts in accident investigation like to cross-check assessments like these – and also refine the analytical methods with new data.  Some of the methods are rough and seemingly not very scientific but that’s hands-on engineering and better than nothing.  If you can measure something – e.g., skid marks, crush shape – even approximately, you can “manage” it; in this case get the speed of the car.

That’s what I was doing last week at a meeting in Moncton of CATAIR, taking part with about eight others collecting data for the continued refinement of an analytical technique.  This time using the skid marks of a body in the grass for determining the speed of a vehicle during an accident.  It sounds complicated but a lot of it boils down to determining the coefficient of friction of a surface like in simple high school physics.

With enough testing, chaps like Mike Reade, Moncton hope results will benefit investigators in situations when they only know the pedestrian’s sliding/tumbling distance after an accident.  The results will be shared with others who work in this field. (Refs 1, 2)

In this case, Mike, who was directing the research and will crunch the data later, threw Skippy, a full size dummy, from a speeding pickup truck driven by Ken Zwicker, Bridgewater.  The rest of us carried out various tasks like spotting where Skippy hit the ground, measuring how far he slid and videotaping what happened to him after he was “hit” by the truck.  Katelynn Everett, a consulting professional engineer from Fredericton, recorded data and did preliminary number crunching.

The field trials are part of the very impressive, ongoing work by CATAIR, the Canadian Association of Technical Accident Investigators and Reconstructionists, and others to refine the analytical methods used by traffic accident investigators. (Refs 2 to 7)

The association is a mix of serving and former RCMP and municipal police officers, professional engineers and technologists all of whom are interested in traffic accident investigation and reconstruction.

In the morning before starting the field trials we met and discussed about 12 different courses on topics related to traffic accident investigation that are available to CATAIR members.

CATAIR meets somewhere in the Atlantic provinces about three or four times a year and do field tests most times.  Recently three teams measured the crushed shape of three different cars that had been involved in traffic accidents.  Each team is analysing speed using different methods and comparing results – Stu Smith, Dartmouth gave a brief report at the meeting on his work on this.  Another time the stopping distance of a vehicle on a road was measured.  And another time still, the turning radius and the path of the rear wheels of a school bus were measured.

Nobody gets paid for this field research.  It’s all to do with refining our understanding of the cause of traffic accidents and reconstructing these, and the camaraderie of like-minded people working together – we do have fun when we’re getting our hands dirty and mud on our boots.

References

1. Reade, M. W. (Mike), Personal communication. June, 2017
2. Reade, M. W. (Mike) and Becker, T. L. (Tony), Fundamentals of Pedestrian/Cyclist Traffic Crash Reconstruction, Institute of Police Technology and Management (IPTM), Jacksonville, FL 2016
3. Civil litigation, forensic engineering and motor vehicle accident reconstruction.  Published September 22, 2015
4. Is your traffic accident investigator well trained, experienced and “accredited”?  Published February 23, 2016
5. “Seeing is believing” at a meeting of traffic accident investigators.  Published March 4, 2016
6. If you  can measure it you can manage it, even if it’s a real mess like a car or truck accident.  Published June 23,, 2016
7. Forensic assessment of traffic accidents.  Published October 26, 2016

What guides civil engineers carrying out a forensic investigation?  What ensures we do thorough work and give an objective opinion – in keeping with the requirements of the judicial system?  There’s usually little on this in the Appendix of an expert’s report so you could be excused for wondering.

There are, in fact, excellent guidelines in place and some are well thought out after decades of development.  They ensure the judicial system is well served.  And they’re enhanced by rules-of-thumb like the following picked up by experienced engineers over the years.

1. Follow the evidence – an old chestnut that – for certain evidence that leads to follow-up investigations
2. If you need more data, get it
3. If in doubt, go deeper, particularly if the foundation soils are involved in a failure
4. Expect the unexpected
5. Beware the tyranny of the obvious when determining the cause of a failure
6. Get your hands dirty and mud on your boots – get out on the site of a failure; no excuses
7. If you can measure it you can manage it, particularly if the failure involves the natural environment as well as the built environment

I thought to mention the existence of guidelines to advocates and adjusters for a while now, particularly when a client is retaining an expert for the first time.  Also when the failure is small or medium sized as most are – not catastrophic and newsworthy – and the budget is small.  The standards are high regardless the size.

I looked through my library and found about three and a half dozen books that have guided me carrying out forensic investigations over the years.  Your eyes might glaze over at such a list.  But take a look at the following selection and be assured that civil engineers are being well guided, particularly by the literature from ASCE and SEAK.

The American Society of Civil Engineers (ASCE) has been guiding civil engineers in practice since about 1857 – 160 years – longer than Canada’s 150 years!  SEAK has been reviewing 1000s of case histories involving experts for more than 30 years, learning from what they read and passing it on to experts.  There’s a lot of guidance out there and a high standard set for civil engineers.  You can see it in the titles of the following::

1. Lewis, Gary L., Editor, Guidelines For Forensic Engineering Practice, 2nd edition, American Society of Civil Engineers, ASCE, Reston, Virginia 2012
2. Greenspan, Howard F. et al, Guidelines for Failure investigation, ASCE, Virginia, 1989
3. Janney, Jack R., Guide to Investigation of Structural Failures, 2nd edition, ASCE, Virginia, 1986
4. Ratay, Robert T., Forensic Structural Engineering Handbook, McGraw-Hill, New York 2000
5. Nicastro, David H., Editor, Failure Mechanisms in Building Construction, ASCE, Virginia, 1997
6. Noon, Randall K., Forensic Engineering Investigation, CRC Press, Inc., Boca Raton, Florida 2000
7. Mangraviti, Jr., James J., Babitsky, Steven and Donovan, Nadine Nasser, How to Write an Expert Witness Report, 2nd edition, SEAK, Inc., Falmouth, Mass. 2014
8. Zinnsser, William K., On Writing Well: The Classic Guide to Writing Nonfiction, 7th edition, Harper Collins, New York 2006
9. Roberts, Donald V., Expert: A Guide to Forensic Engineering and Service as an Expert Witness, Association of Soil and Foundation Engineers, ASFE, 1985
10. Speight, James G., The Scientist or Engineer as an Expert Witness, CRC Press, Boca Raton, Florida 2009
11. Cohen, Kenneth S., Expert Witnessing and Scientific Testimony, CRC Press, Boca Raton, Florida 2008
12. Babitsky, Steven and Mangraviti, Jr., James J., The Biggest Mistakes Expert Witnesses Make and How to Avoid Them, SEAK, Inc., Falmouth, Mass., 2008
13. Stockwood, Q.C., David, Civil Litigation, 5th edition, Thomson Carswell, Toronto 2004

I don’t expect you to check out these references too thoroughly, certainly not read them. Just know that civil engineers are guided by good literature on how to carry out thorough forensic engineering investigations and render objective opinions.  And experienced engineers have their rules-of-thumb.

A thought: What guides your expert carrying out a forensic investigation in their field of study if s/he is not a civil engineer?