Common techniques used by collision investigators to investigate road traffic
collisions and explain the science used in each technique.
Equipment used to record a collision site:
Many techniques used to reconstruct a collision, depending on the severity of the collision,
will depend on the techniques used by the investigators. Experienced and trained
investigators will evaluate the collision scene using the following techniques:
Scene of crime kits:
Crime scene investigation is a messy job, it involves substances of potential harm, bodily
fluids, soil and debris. All investigators, including traffic investigators, should take the
necessary precautions to ensure their safety. One of the most important parts to any
investigators kit would be full PPE. Not only does this protect the individual, it also protects
evidence from contamination. In addition, it protects evidence continuity alongside
precautions to keep the investigators safe. These pieces of equipment should be disposed of
after the crime scene has been investigated and a new crime scene kit must be provided to
the investigators for the next crime scene. Crime scene kits also include the necessary
equipment needed to collect evidence from the crime scene. This kit makes sure tha\t the
investigators have all the equipment they require in order to thoroughly investigate and
examine the scene without missing a step.
Camera and tripod:
Documenting a collision scene is a must, using a high quality digital camera each time a
collision happens. Evidence of the crash scene must be documented prior to any collection
of evidence. Cameras can be used to document all aspects of a collision scene and are
commonly photographed alongside measuring tools to provide aspects of size. All cameras
that are used to photograph a scene must be of high resolution, this allows all images to be
clear. Furthermore, to assist clear images, collision investigators often use a tripod, this
prevents the images from being blurry. If a photograph is fuzzy or blurry due to the
photographer's shaky hands, it jeopardises the image being used in court. Commonly, to
prevent this, tripods are used to capture large areas of a collision scene and create clearer
photographs to be used as evidence in court.
Photography
Photography is a key method in order to preserve and document road traffic evidence.
Nowadays, digital cameras allow all photographs to be taken with high quality. By
photographing a road accident, it allows investigators to create a complete and detailed
reconstruction of the scene for further understanding of the events that took place.
Photographing a collision scene must be done thoroughly, covering the entire scene.
Commonly, photographs will be taken of small details, highlighting the specific damage to
the vehicle, but not identifying the side of the vehicle which was damaged etc. Without
detailed photographs, it is hard to understand the force of impact, damages to the vehicle on
specific parts eg. left front tyre and even the direction the vehicle moved after impact.
,Metrology instruments:
Measuring equipment
Measuring equipment is commonly used alongside photographs, it can measure skid marks,
vehicle damage and other important details. In some cases, measuring wheels and tapes
can be used to measure the entire collision site, this is useful as it measures the whole area
of the site. Commonly, to prevent misconceptions of damages to the vehicle, measuring
equipment can be placed next to evidence to provide measurements to create a better
understanding of certain pieces of evidence such as the length of a skid mark. Whilst this is
useful to create a better understanding of certain pieces of evidence, measuring equipment
isn’t always accurate. This can take much longer to document the evidence, and in some
cases is more dangerous if the collision site occurred on busy roads like motorways.
Wax crayons
Wax crayons can be used in collision investigation. Often, circles are made to highlight areas
of damage to the road surface possibly before and after the collision. Wax crayons can also
be used to mark and record specific skid marks which may later identify the direction of
travel etc. Tracing paper can be used to create sketches of the collision scene or just the
vehicle itself. It can also be used to create replicas of the skid marks or damages to the
vehicle.
Scientific calculators
Scientific calculators are commonly brought to collision scenes. When investigators are at a
collision scene, after collecting all the evidence and beginning to piece the events together,
they can begin to calculate the speed the vehicle was travelling at before the collision. To
calculate these speeds, the investigators will use their scientific calculator and use what they
have gathered from the scene to calculate these. Not only does it determine the vehicle's
speed, it also allows investigators to understand how the collision happened, it can
determine the reasoning for the human and vehicle rest position and finally can suggest why
the vehicle has certain damages.
Modern survey equipment
Modern surveying equipment is another technique used to investigate road traffic collisions,
it allows for data points to be recorded with high accuracy and quickly. There are a few
variations of the survey equipment, but the most common one would be Total Station. Total
station uses a laser, measuring the distance to a prism which is mounted to a pole. As there
are many variations, some survey equipment doesn’t use a prism and can measure surfaces
instantly. Devices without prisms can be useful when measuring data on busy roads or
motorways The science behind laser surveying equipment is the emission of a laser from a
rotating mirror facing outwards to the area being scanned, or even the area of the collision.
The laser beam is reflected back to the scanner by objects passing it such as a moving or
standing vehicle. The distance is then calculated, the time taken for the laser to travel and
, the speed are both known values. As a result, the distance is then recorded on a memory
card so the data is safely accessed and secured for later analysis.
Modern surveying equipment allows data points to be collected such as speed
measurements, one million points per second, it provides speed, accuracy and easy
understanding of the results.
Photogrammetry is the use of programs to reconstruct a scale model of the collision site and
uses the photographs collected at the accident. A common program which is used is
Photomodeler, it documents evidence on the road where the accident occurred which would
have made the road unsafe before the crash. If the original vehicle is no longer available,
using the photographs taken, a full reconstruction of the accident can be created.
Photogrammetry allows evidence which couldn’t be collected like tire marks to be
reconstructed, this is a time consuming method and is slightly more difficult to achieve in
comparison to other methods, but when carried out is mostly accurate. When photographs
were taken at the accident site, the use of a photomodeler must be considered, as they
must be taken for the photomodeler to work best.
Photomodeler can be used in two ways, roadway uses and vehicle uses. Roadway uses
include paint marks, tire marks etc which can be seen on a busy road.Photographs would be
taken of the evidence (for example a skid mark), the photos are then loaded to the
programming. A scale drawing of the scene will then be made from the photos, as well as a
birds eye view drawing.
Vehicle use for Photomodeler is when a damaged vehicle is examined. The investigator will
take photos which will later be downloaded to the photomodeler software. Often, a vehicle
will have to be photographed using photogrammetry rather than other methods due to the
time restrictions. After the programming is downloaded, investigators can make a 3D model
of the vehicle to show the damages inflicted on the vehicle.
Another technique is 3D scanners, it works similarly to Total Station. The 3D scanner is
placed on a tripod, it makes a 3d model of the surroundings and highlights small details. All
scans can be taken from all directions, so out-of-sight views can be scanned as well. To
overcome the limits of a single scan, multiple scans can be made and are programmed to
create a 360 degree view of the area. One limitation to 3D scanning is that it can’t take
scans of a hidden damaged vehicle. The scan may miss out gouge marks or debris from the
vehicle hidden in the grass. Whilst this must be considered, it is useful to help reconstruct a
360 of the accident site.
The last recording technique is a Black Box. Many new vehicles contain a black box which
can be used to reconstruct an accident. The information can be gathered from the vehicle,
by downloading the CDR download, it can be used to reconstruct an accident. The only
problem with a black box, it may record the vehicle travelling at 70 mph when in reality it was
travelling at 30 or 20 mph but the vehicle's tyres were spinning. Black boxes show the speed
the car travelled, and each time the driver reaches above the speed limit their car insurance
would increase by a certain amount depending on the amount of mph they travelled higher
than the speed limit.
