Forensic assessment of traffic accidents

It doesn’t matter how big the mess, if you can measure it you can analyse it, at least approximately.  Nowhere is this more true than for traffic accidents.  The following illustrates this and how simple it is.  It’s also important for litigators and insurance consultants to get some idea of the accuracy possible.


You’ve all seen the condition of a car after an accident.  You could be excused for asking how anyone can get information on the speed of the car(s) at the time of the  accident from such a mess – a factor in some insurance and civil litigation claims. Yet experts do this.

It involves measuring the crushed part of the car at key locations – the damage relates to the change in speed at the time of the accident.  These measurements are then referred to published and proprietary crash data by various sources for the make, model and year of the car.  The National Highway Traffic Safety Administration is one source.  Finally, putting the relevant data from these sources in a mathematical formula to get information on speed at the time of the accident.  Laborious but fairly simple.

Widely used formula have been worked out by others and are usually not a concern to the mess measurer at the accident scene.  The formulae have a semi-empirical basis – their development is based on both observation and theory, like much in hands-on engineering.  Hence the approximate nature of the answer on speed.


The measuring procedure is not too much different from that followed by a land surveyor measuring the height of the ground at key locations.  The surveyor references the measured heights to a provincial grid then uses the heights to make a map of the land.  In fact, total stations land surveying equipment is used by some forensic experts to measure – “map” a crushed car.  The shape of some ground surfaces can also be quite messy, like cars after an accident.

The map or shape of the ground, along with other information, can be used by experts (geo-morphologists) to determine why the ground has the shape it does.  Similarly, crush measurements along with data from published sources can be used by experts to determine why the crushed car has the shape it does.  What was the speed to cause this?


I assisted Dr. Stu Smith, C. Tyner and Associates, Halifax take these types of measurements on three cars – a Ford, a Buick and a Nissan, during a meeting of CATAIR in Moncton recently.  The cars had been in real traffic accidents.  Dr. Smith was carrying out a practical exercise – a laboratory test of sorts.

This was a follow-up to a lecture on this type of analytical procedure by Mr. Jason Young, P.Eng. of Advantage Forensics, Inc, Toronto.  Mr. Young gave the lecture during a CATAIR meeting last June in Moncton. (Ref. 1)  Stu and I were doing our homework after the lecture along with others at the most recent meeting.

We laid out a “box” grid on the floor around each of the three cars, simulating the grid used by land surveyors.  Measurements were then taken to the crushed steel bumper beam in each car referenced to the rectangular grid.  Stu and the others at the meeting use their respective measurements along with the published data and a formula to get information on speed when the car crashed.

Steel beams have been built in cars in recent years for this very purpose – in the event the car is in an accident.  Even more recently, data recorders have been installed in new cars to get information on speed in case of an accident.

Findings on speed for the three cars by three different teams of people using different formulae will be compared with speed information from the data recorders in the new cars assessed in our homework.

I have a good interest in the results of empirical methods in getting an approximate answer to a problem.  Empiricism is all around us in the built environment.  Theory is in the text books.

The data recorder in new cars is also certain to have an empirical element – and we expect these results to vary too.  It’s the best we can do with messy cars after a traffic accident.  But we can do something with simple measurements as I’ve explained, whether with a tape or a data recorder.

(Dr. Smith looked at this item before publication and made helpful suggestions)


  1. 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
  2. Is your traffic accident investigator well trained, experienced and “accredited”?  Published February 23, 2016
  3. “Seeing is believing” at a meeting of traffic accident investigators.  Published March 4, 2016

“Crewing” on a forensic drone flight

I continue to be impressed by the possibilities of forensic aerial photographs taken from drones of the locations of engineering failures and accidents.  Most recently when I learned that I could fly as “crew” on a drone and take the photographs myself.

I’ve used Robert Guertin of Atlantic Camera Man Ltd. in the past to take aerial photographs of sites that I’m investigating.  Robert flew the drone and took the photographs as I directed from a distance off to the side.  There’s a risk with this technique, however, of something being lost in explaining the photographs wanted.

Robert told me recently that he now has a drone that allows me to seem to fly as crew on the drone and take photographs when we’re aloft.  He demonstrated this last Saturday morning.  He flew the drone and I operated the camera from a station nearby.

I took standard orientation-type photographs from the four points of the compass from a distance and also up close.  Then I took video as the drone slowly descended from an altitude of 385 feet to 8.5 feet – note the precision in the altitude – stopping just above a duck on a rock in a pond.  We didn’t want to spook the little fella with the whirling sound of the drone’s rotors as he preened.

The drone is held so steady by GPS on board that the only way you could know it was video was the moving traffic on a nearby road.  Resolution was good enough to see the different coloured feathers on the duck’s back.

There’s no question I’ll use this drone and take the photography myself on my next forensic site investigation.  It’ll be remiss of me not to.


Drones are being used increasingly and in diverse industries.  The Globe and Mail reported a week ago on the following industries in decreasing order of potential drone-powered solutions, and a couple of years ago in a more descriptive way: (Refs 1, 2)

  1. Infrastructure                  $45.2B
  2. Agriculture                      $32.4B
  3. Transport                         $13B
  4. Security                          $10.5B
  5. Media/Entertainment       $8.8B
  6. Insurance                        $6.8B
  7. Telecom                          $6.3B
  8. Mining                             $4.3B

Forensic drone photography is likely to be used most often in the infrastructure and insurance industries.  Areas where engineering failures and personal injury accidents occur.  But drone photography is getting increased use in all stages of engineering: Planning, design, construction, inspection, and maintenance of structures.

As well, traffic accident sites in the built environment.  Yesterday I attended a meeting of CATAIR in Moncton. (Ref. 3) I learned that at least one traffic accident reconstructionist has a drone and is taking aerial photographs of traffic accidents.

There’s a good review in the article Drones and Engineering by Bill Corbett in the June/July issue of Canadian Consulting Engineer. (Ref. 4)

Not to be outdone by activity on shore, oceanographers at Dalhousie University are using drones to “fish” with – to locate and track the rare North Atlantic right whale off the Atlantic coast. (Ref. 5) I learned a couple of years ago that drone pilots have no hesitation flying over water, these flying machines are that well developed and reliable.

I saw it again last Saturday when Robert demonstrated how I could photograph a site myself from his drone, and over water if I want such a shot – see the preening duck above.

I will have no hesitation about flying as “crew” the next time I personally take aerial photographs and video from a drone during a forensic engineering investigation.  You must ensure your expert examines your site this way – many cases lend themselves to this forensic photographic technique.


  1. The Globe and Mail, Send in the Drones,  Saturday, September 24, 2016, Report on Business Weekend, page B6
  2. The Globe and Mail, Rise of the Drones, Monday, April 7, 2014, Report on Business, page B1
  3. Canadian Association of Technical Accident Investigators & Reconstructionists (CATAIR)
  4. Canadian Consulting Engineer, Drones and Engineering, June/July 2016 page 23
  5. The Chronicle Herald, Right Whales: Elusive Habitat May Be Found, Thursday, September 29 2016, page A5