Nearly all crashes have some visibility aspect in question. A motorist may fail to notice an approaching train or pull out in front of a vehicle not realizing the hazard or appreciating visual cues present within the scene.
During our site investigation, we document the location photographically, and may use our total station to map the terrain and other pertinent data. Also, if adequate lighting is at issue, the site would be documented using a state-of-the-art photometer. This allows quantitative measurements in addition to qualitative observations.
In addition to performing visibility investigations, Kevin Johnson teaches along with Jim Sobek, P.E. at Clearly Visible Presentations. In these courses, students learn the physics behind lighting and also learn how to document scenes with difficult illumination.
Only 50 feet from the near rail looking toward an approaching train. The sight line limits the ability for a motorist to observe the approaching train. Without seeing the train the vehicle crossing the track is unable to yield to its right-of-way.
In this photograph, the high intensity lamps on the front of the locomotive are the only visual cue a train is approaching. A vehicle traveling 20 mph will arrive at the crossing in only 2 seconds. The approaching high speed train will arrive at nearly the same time.
Were the headlamps on? Were they off? A forensic lamp analysis can determine if they were illuminated at the time of the crash.
Headlamps produce a distinct pattern on the roadway. The intensity of each portion of the beam is defined by Federal Motor Vehicle Safety Standards. We use these standards or map the pattern of the actual vehicle to determine how much illumination fell upon an object or pedestrian. We then analyze this to determine if sufficient light was present for an object to be visible.
In this photograph, (a self portrait of a Wisconsin State Police Trooper) a process involving a very long time exposure captures the geometry of a scene without the aid of a flash or nearby lights.
In this photograph of the same scene only a flashlight is used for illumination.
This is a generic term used to describe the process of utilizing math, physics, and the scientific method to determine the dynamics of a collision that has occurred.
As an Accident Reconstructionist, we are often called upon to identify the contributing causes of a collision. This may include driver, vehicular, and roadway issues or a combination of factors.
The Laws of Physics are applied to the analysis so that it is reproducible, commonly accepted in the scientific community and accomplished to a degree of scientific certainty.
The process typically starts with the site documentation. During this part of the investigation, the roadway is inspected for damage and evidence of the collision. Photographs are taken and measurements are made documenting the tire marks, scratches, gouges and other debris that may have been left as a result of the impact.
Vehicle exams are performed to determine the extent of damage to the vehicles involved and to look at specific components. Many vehicles have data recorders that can be imaged and analyzed. In addition head lamps, tail lamps and other lights may be inspected to determine if they were illuminated at the time of an impact.
Throughout the discovery process other data, statements, depositions, and other evidence is gathered and analyzed. At the conclusion of the investigation, the goal is for you to have a better understanding of the facts of the case and to have a resourse to explain these scientific principals to your audience. This can be accomplished through demonstrative graphics, a written report or through deposition and trial testimony.