The Complete Guide to Accident Reconstruction
November 15, 2021
Our collision reconstruction experts have worked on thousands of cases, making them industry leaders in terms of knowledge and experience. We’re here to provide a comprehensive understanding of how collision and accident reconstruction works.
There are 4 Levels of Collision Investigation:
Level 1: Every police officer undergoes level one training and can investigate collisions that do not cause serious injuries and they are able to collect basic data.
Level 2: Scene Collision Investigators go through a one-week course and are trained to do more than evidence collection. They perform evidence preservation and perform basic math.
Level 3: Technical Collision Investigators are part of a collision construction unit after completing a three-week course. They compile technical data, come up with the equations and solve the math involved in the actual collision.
Level 4: Professional Collision Reconstruction experts determine the immediate cause of a collision. One of the major differences between level four and level three reconstructionists and experts is that a judge or justice of the peace, depending on the courtroom, can authorize a level four reconstructionist and expert, allowing them to offer potentially unbiased evidence. They submit the final report and conduct interviews.
The Three Phases of Collision Analysis
This takes into account various factors prior to the incident including the mechanical aspect of the vehicle if something was wrong with it, the condition of the tires, etc. These help determine the events better.
The sequence of events that actually occur at the time of the collision.
Post Collision Analysis
This is where collision investigators come in to analyze the data presented, obtain more information from witness statements and review cameras to help determine why the collision occurred.
Case Studies: A Dive Into Actual Collision Sites
Case Study 1: Vehicle Vs Vehicle
The Pontiac Montana hit the front driver’s side of the Volkswagen bug. The driver of the Volkswagen bug received grave injuries due to the collision.
The vehicle in the red box denotes the Pontiac Montana heading southbound at about 60 km/hr. The vehicle in the blue box denotes the eastbound Volkswagen bug which is also traveling at somewhat the same speed at about 50 km/hr. The Volkswagon bug is subjected to a stop sign as well as a painted stop bar on the road.
The green area with the dots denotes a forested area and it is the first Point of Possible Perception (a place and time at which both vehicles could have perceived the hazard).
The Point of Actual Perception is the time and place at which the hazard is actually perceived. Studies have shown that the delay between the Point of Possible Perception (the point when you could have seen the hazard) and Actual Perception (the point when you actually see the hazard) is about three-quarters of a second (0.75 seconds). This is known as Perception Delay.
In this time frame of three-quarters, the vehicles are moving. The Pontiac has traveled an additional 12.7 meters and the Volkswagen Bug has traveled 11.3 meters.
The next step is Reaction: an involuntary response to the hazard. It could be steering the car in another direction or putting the brakes on to prevent the impending hazard.
Reaction Time is the time between the Point of Actual Perception and the Reaction which again is three-quarters of a second or 0.75 seconds. During the reaction time, the vehicles are still moving. The Pontiac has covered 12.7 meters and the Volkswagen has covered 11.3 meters. This is known as the Reaction Distance (the distance traveled during the reaction time).
The Action Point is when a person makes a decision and puts it into action based on the perceived hazard. In this case, the action point is the Pontiac putting on the brakes. He’s taking Evasive Action to avoid the collision. The Evasive Action Distance is the distance traveled from the action point to the area of impact. During this time the car has slowed down due to the brakes. The Pontiac Montana traveled an additional 20.9 meters and the Volkswagen traveled 16.4 meters both covering the Evasive Action Distance.
Engagement is the penetration of one traffic unit into another object or traffic unit. The Pontiac Montana collided with the Volkswagen at the front of the driver’s door.
The Final Position is the location where the traffic object or unit comes to rest after the collision. The Level 4 investigators were able to work back the collision using the formula of momentum and mathematics to scientifically prove that the Volkswagen bug did not stop when it came to its stop sign and entered the path of collision with the Pontiac Montana and it was easy to determine who was at fault during this collision.
Case Study 2: Motorcycle Collisions
There are a few differences between two-wheeled vehicle collisions and four-wheeled vehicle collisions and how they play out on the road.
- The handling dynamics are different
- The occupant kinematics differ as with car collisions you are inside the car, seatbelted, whereas with motorcycles you are sitting exposed (hopefully with a helmet)
- Performance: people riding bikes are much more capable performers
- Visibility is different with the presence of a helmet
- Generation of different tire marks on the road
All of this is taken into account when reconstructing a collision involving motorbikes.
In the evening, a motorcycle crashes into the rear end of a Toyota Corolla.
The motorcycle rider claimed that the Toyota Corolla pulled in front of him, causing him to strike. The green pylons indicate the pre-collision tire marks from the motorcycle. The rider perceived the potential hazard and applied the brakes, however it was not done in time, as shown by the length of the skid marks.
The scratch on the road across the orange pylons was due to the bike overturning to its side after the collision, with the footpeg of the bike scraping against the road. The pool of gas indicates where the motorcycle came to a halt.
The crash site showed that the car driver’s seat was covered in glass. If there was someone sitting in this vehicle, it would not have had as much glass present on the seat. This disproves the rider’s story that the car pulled in front of him. The bike in fact ran a traffic light and collided with a car parked on the side of the road.
The helmet or at least images of the helmet after the crash shed light on a lot of facts. It helps determine what happened to the rider after the crash and match-up injuries. The scratch marks on this helmet are on three different angles helping explain what the wearer of this helmet experienced after being ejected from the bike post-collision.
Case Study 3: Pedestrian Collisions
In order to understand the impact of a vehicle-pedestrian collision, it is essential to understand the complete series of collision events. Accurate information needs to be gathered as soon as possible. This information includes:
- Physical Evidence such as photographs, measurements of tire marks, rest positions, bloodstains, vehicle damage, and other similar debris
- Traffic Collision Report
- Statements from all witnesses and involved parties
- Detailed medical reports of the pedestrian’s injuries
This is a rural road with a speed limit of 60 km/hour. The motor vehicle was traveling westbound. The pedestrian was coming eastbound.
There can be two types of pedestrian collisions:
- The wrap collision is where the pedestrian is hit by the front of the vehicle. The hood and the windshield are damaged as the pedestrian rides on the windshield and hood until the car comes to a stop and the pedestrian gets thrown off the car.
- A throw collision is when someone goes over the top of the vehicle.
This is a wrap collision case and the pedestrian was thrown forward.
This evidence is from the pedestrian himself showing the footwear and marks of being struck. The pedestrian was on the travel portion of the highway when he was hit by the vehicle. This was the driver’s fault.
Case Study 4: Commercial Vehicle Collisions
The reconstruction of motor vehicle collisions requires specialized training beyond the average traffic collision reconstructionist. They must possess:
- Detailed knowledge of the Transport Canada safety regulations
- Detailed knowledge of the mechanics of a commercial vehicle
- The ability to identify and address trucking safety issues
- Detailed knowledge of the dynamics of a commercial motor vehicle
The reconstructionist inspects vehicles that show deficiencies ranging from brakes to steering, and load security issues, and studies e-logs or logbooks to determine driver error caused by fatigue.
This is a parked trailer tractor where the driver was offloading cars but he was fatigued due to being past his duty time. When offloading a car positioned at the front, the hydraulic system is supposed to be up and safety locks need to be in place. The driver forgot to do that, due to fatigue.
This caused the car to go off the front of the tractor-trailer and fall on its back. The driver sustained major injuries as he was not wearing a seatbelt. The investigation showed that he was over his log time, which is why investigating the logbooks is essential.
Review of Documents and Analysis of Evidence
One of our investigators receives an assignment from an adjuster or a lawyer involving a motor vehicle loss. It will be the investigator’s responsibility to complete an unbiased objective analysis of the provided documentation for review in order to assist the client in reviewing the events contained therein.
The assignment covers a two-vehicle collision on a rural road. The cars are a Camry Sedan vs a Ram Truck. Both drivers stated that the other crossed the center line and into their respective lanes of travel.
Reviewing the Documents
The investigator receives all of the records and evaluates them to establish the mitigating factors that led to the collision:
- Collision Report: In this case, it was a collision level 1 report, a basic motor vehicle action report. If it was a level 2 report, they would go beyond what happens at level 1, such as a field sketch which provides more details that could be missed such as perishable evidence
- Court files and court proceedings
- Driver’s actions, driver’s testimony, any statements taken
- Attending officer’s observations and evaluation of the collision scene
- Attending officer’s notes
- Weather conditions at the time of the collision, data from nearby weather stations
- Detailed analysis of scene photographs taken by not just the police attendants but also by the plaintiff and the defendant, lost photographs, dashcam records
- Condition of vehicles, tire conditions, roadway evidence
Despite having visited the site of the incident a year and a half after the collision, our investigators still found roadway evidence in the form of debris from the car and where the vehicle struck the rock. This artifact evidence can be reviewed to objectively relay the course of events that occurred.
The Toyota Camry was heading southbound and the plaintiff (the Camry) said that the defendant’s Ram slid sideways, crossing over the center line and striking the Camry with her passenger side.
The scene and the photographs provided by the adjuster were examined to uncover the events. After studying the lost photographs, it was evident that the primary damage to the Dodge Ram was to the front end and not the passenger side as stated in testimony. The plaintiff’s testimony was not supported by the physical evidence.
Vehicles can be examined if they are available, even if it’s in a scrapyard. Investigators look out for the following clues and evidence:
- Tombstone Data
- Exterior Damage
- Interior Examination (If the seatbelts were worn and if the occupants moved around during the collision.)
- Tire and Rim Examination
- Lamp Examination (If the wire connected to the brake or headlamp heated up, implying if they were applied or not.)
Aerial mapping can be done via a drone to gather measurement grades and evaluations. The above photograph was taken by the investigator at the scene and was able to find gouge marks consistent with the collision at the scene of the incident.
Through drones and a program called Drone Deploy, it is easy to collect evidence and analyze it. In this case, 161 photographs were taken and Drone Deploy helped stitch the images together to make sense. You can get an entire overview of the scene, zoom into specific points, and generate a 3D model. A few advantages of this technology and approach are:
- It is possible to come back later and take slope and scene measurements
- The data is real-time and the photos are timestamped, proving to be an upgrade over outdated Google Maps
- Create a point crowd
- You can export data for AutoCAD and diagramming
- Create 2D and 3D models
- View panoramic photos
(Difference in quality between Google Maps and Drone Display)
(Image Quality from Drone Capture)
(3D Model Reconstruction)
Crash Data Retrieval System
The Crash Data Retrieval Systems (also known as the black box of the car) has been mandated in the car and light-duty trucks sold in North America since 2013. They are monitoring what’s going on in the vehicle. They are the brains of the airbag and if they detect a change in velocity, they are alerted as to whether to protect the occupants of the car by engaging the airbag. While making these decisions, it records the data.
The CDR is an unbiased and accurate source of technical information to analyze what happened seconds before, during, and after the accident or incident.
The mandatory data points collected by the CDR System are:
- Impact severity is measured by the change in velocity
- Vehicle speed up to 5 seconds prior
- Steering or accelerating input (90%, 80% throttle)
- Brake input
- Ignition cycle
- Seatbelt status
- Airbag deployment
Conclusion and The Final Report
The final report talks about all the facts and evidence that have been reviewed during the investigation. It includes:
- Scene Evidence
- Scene Examination
- Vehicle Inspection
- Crash Data Analysis
All the available data, information, and documentation are evaluated and an objective, the conclusive report is prepared. The report consists of a summation of events from a conclusive perspective in a post-analysis review format which is then presented to the client.
Reaching out to Origin and Cause for Accidental Investigation
If you’re reaching out to Origin and Cause for an investigation assignment, the following documentation would be extremely insightful and helpful:
- Photograph package (from the involved drivers, police photographs)
- CDR information (if it involves Level 3, Level 4 Investigation)
- Reconstruction reports
- The inspection report was curated by a loss adjuster
- Field sketches if available
- Officer’s notes
- Court documents
We will help you get to the root cause of the accident by relying on scientific methodology and testing and basing our conclusions only on facts.