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The role of human factors in analyzing accidents and injuries

What we sense, how we process, how we react

Human factors is how we perceive and interact with our environment. Understanding human factors can play a key role in weaving together a complete accident reconstruction by providing vital information linking complex events.

Dr. Strauss showing volunteers a reconstruction of an accident
Dr. Strauss performing human factors research with volunteers.

Dr. Strauss has the extensive knowledge and experience to understand human factors and how to apply that to solving an accident event. In a simple model, human factors are the inputs to our senses (typically vision, hearing, touch, orientation and olfaction), the cognitive processing that takes place in response to inputs, and the resulting actions (limb movement such as: running, braking, deflection, head positioning or yelling). Unlike dimensions that can be referenced, such as the vehicle length or bumper height of a 2014 Chevrolet Camaro, individuals are unique in their anatomy and physiology, as well as their responses. It is likely that an 80 year old driver would have diminished vision and hearing, would have slower cognitive and reflex actions, and may also have less strength and range of motion compared to a 30 year old, even though they both weigh the same and are of the same height.

Scenario 1: A child runs out into the street.

An accident where human factors can provide valuable information in the accident reconstruction is in the analysis of an 8 year old boy who runs onto a roadway.

  • What is the 50th percentile running speed of an average 8 year old male? This speed directly affects the time available for a driver to see, perceive and react.
  • Did the event occur in the daytime or nighttime, or was it raining, which affects the visibility of the child?
  • Were there obstructions in the line of sight between the driver and the child, and if so, how many and how large?
  • Was there glare in the driver's eyes from on-coming headlamps, the sun, or artificial illumination?
  • How much background visual clutter existed, which could distract the driver from recognizing the child earlier?
  • Was the driver distracted or impaired by chemical use or electronic devices thus slowing his perception and reaction times?
  • What opportunities did the driver have to take evasive action such as steer right (into a tree?), steer left (into on-coming traffic?) or brake hard?
  • Was this a simple or complex perception - reaction event?

Scenario 2: Construction worker injured by dump truck.

Video sequence of a fork lift accident
A surveillance camera records a forklift truck accident that occurred just as it exited the refrigerated portion of a warehouse through a plastic curtain and struck and injured a pedestrian. The video can be analyzed to determine forklift speed, visibility of the forklift, and the perception and reaction time of the pedestrian. Further work involved quantifying the sound from the forklift backup alarm and visibility of the strobe light.

Similarly, in industrial or construction settings human factors can also play an important role in reconstructing an accident. If a dump truck is backing up and strikes a co-worker, it may be necessary to examine whether it had a back-up alarm. If so, was the alarm in-fact working, and in a quantitative manner, how loud was it? Were there other vehicles in the vicinity that were backing up at the same time, and also had their backup alarms sounding which could have masked the sound from the dump truck? Did the event occur near a building where brick walls caused echo and reflection of the alarm sound, or other sounds? Did the construction vehicle cause ground vibration which could be felt by the pedestrian, and later measured during testing? Was the driver or pedestrian preoccupied, distracted, new on the job, well trained, over-worked or medicated?