Collision Investigation

In the beginning…

The first recorded motor vehicle related fatality occurred in 1869 in County Offaly, Ireland, when Mrs. Mary Ward fell from a steam powered carriage and was crushed under one of its heavy iron wheels (1). The resulting coroner’s inquest was far from a scientific examination. The jury concluded from eye-witness testimony that Mrs. Ward, lacking something to grasp, had fallen from the carriage while it was travelling at an impressive speed of 3.5 to 4 mph (5.6 to 6.4 km/h).

173 years later

Motor vehicle technology has come a long way since the time of Mrs. Ward’s tragic end. So have the techniques and equipment used by today’s professional collision investigators and reconstructionists. Investigators are often able to use the available evidence to determine what occurred even when there are no independent witnesses, or when witnesses give conflicting versions of the events.

Evidence

The first and primary role of a collision investigator is gathering evidence – the pieces to the ‘puzzle.’ The more pieces of the puzzle that can be found and fit together, the clearer the picture of the crash becomes. There is very little a collision investigator, or a reconstructionist, can reasonably conclude without enough, reliable evidence.

Being Proactive

The best time to collect short-lived evidence is at the ‘live’ collision scene, when it is the most plentiful and the least contaminated. One of the most common problems facing collision investigators and reconstructionists is that they are often hired weeks, months and even several years after the crash they are hired to investigate. This often means that important live scene data, photos and vehicle damage measurements is collected by others – if it is collected at all. It is difficult, if not impossible, to give meaningful comments and opinion about a crash when there are no longer any vehicles available to inspect, the crash site has been repaved and the witnesses’ memories are fogged by time – or by pending legal action.

Collision investigators must be able to prioritize and work quickly to properly document a live scene. Inclement weather can rapidly put a foot of snow over critical evidence, or wash it away with heavy rain. The actions of emergency services, efforts to recover damaged vehicles and even bystanders can dramatically reduce what evidence is available at a scene. Fire fighters often cut up vehicles to extricate occupants, sweep away vehicle key debris evidence, hose down vehicle fluid trails and run over tire tracks – causing physical evidence to be lost or destroyed. Short-lived evidence, such as tire marks, debris and fluid trails, can also disappear with the movement of traffic. Failure to mark and record the final resting positions of the vehicles and bodies can severely hamper any future efforts to reconstruct the crash.

Sometimes, it is not possible or practical to examine a site while the vehicles are still there; however, the sooner this work can be completed, the better. In the days after a crash, maintenance crews can replace crash damaged utility poles and broken signs, patch deep roadway gouges, re-grade shoulders. Affected homeowners can fix damage to buildings, fences, yard features, sod, or remove damage and debris.

Black Boxes

Given the inherent limitations of witness testimony, investigators have used science and technology to find other means to establish and confirm the events of a collision. One of the most important recent developments for collision investigation and reconstruction has been the wide scale use of onboard data recorders in motor vehicles – from passenger cars to heavy commercial vehicles.

Event Data Recorders (EDRs), sometimes referred to as ‘black boxes,’ are installed in most late model passenger cars, light trucks and/or SUVs equipped with airbag systems. EDRs typically capture data that is used to decide whether and how to deploy airbags during a collision. It can also capture data during the crash event.

EDR data can simplify the process of determining what happened during a collision and who was at fault. This is admissible as evidence in court. EDR data can often be analyzed to help provide details about the crash and the occupant restraint systems, such as:

• driver actions just before a crash (reasonable… or not );

• pre-impact vehicle speed;

• measures of crash severity;

• the status of the seatbelt restraints (buckled… or not); and

• the functioning of the airbag system.

EDR data can often be read by investigators using a commercially available download tool. What data gets captured is greatly dependant on the vehicle make, model and year. Not all cars have EDR data and they are not required by law, but the number is growing significantly. Pending regulations in the US regarding EDRs will likely result in even more data becoming available for download in the future.

Total Station

A total station is a surveying instrument capable of electronically measuring and recording angles (horizontal and vertical) and distance to selected points. They are ideal for quickly and efficiently recording the geometry of the roadway and the relative location of vehicles, evidence and other objects of interest within a collision scene. Being stored digitally, the scene can then be generated as a scene diagram or a 3-D model using a computer.

Total stations can also be used for taking precision measurements of damaged vehicles. These measurements can be used to create 3D models of the involved vehicle that can be stored. These 3-D models are then available for analysis – sometimes long after the actual vehicle is no longer available for measurement.

Photogrammetry

Photographs are very often the only source of critical evidence. A technique called ‘photogrammetry’ can sometimes be used to obtain required measurements from photos taken at a crash scene, or of the involved vehicles. This technique is especially valuable if no one thought to, or was able to, take scene measurements. The fundamental principle used by photogrammetry is triangulation. By taking photographs from at least two different locations, so-called ‘lines of sight’ can be developed from each camera to points in a collision scene. These lines of sight can then be mathematically intersected. With sufficient data, photogrammetry can be used to create 3-D coordinates for a crash scene.

Animation

For particularly complicated files, it can be challenging to translate findings from ‘techno-garble’ into something that most people can understand. Computer animation is often useful in this regard. A multitude of vehicle types and scenarios can be animated. The relative positions of all the involved vehicles can be shown for the critical seconds leading up to and after a crash. Animation is also useful for showing various collision scenarios, typically when there is conflicting testimony or when exploring ‘what if’ scenarios.

Why hire a collision investigator or reconstructionist?

Police reports often fail to answer critical questions about a crash from the perspective of civil litigation. The focus of a police investigation is often limited to a basic determination of ‘who’, ‘what’, ‘when’ and ‘where’, along with a cursory attribution of fault. The ‘why’ and ‘how’ of the crash is often left unexplored. These questions often require private collision investigators or reconstructionists to answer.

End Notes

1.    “Mary Ward 1827-1869”, Offaly Historical & Archaeological Society, Bury Quay, Tullamore, Co. Offaly, Ireland, http://web.archive.org/web/20060
105215309/http://www.offalyhistory.com/content/reading_resources/famous_people/ward_mary.htm