Tag Archives: Collision Reconstruction

Automatic Emergency Braking Doesn’t Always Prevent Pedestrian Collisions


Breaking Technology

Robert T. Lynch, PE, Principal Collision Reconstruction Engineer

Automatic Emergency Braking (AEB) is generally designed to automatically apply the brakes when a rear-end vehicle collision is imminent. This technology has been shown to mitigate rear-end impacts; however, this technology is not always capable of detecting pedestrians crossing in front of a vehicle.

AAA has conducted testing of vehicles equipped with AEB and found that in 60% of the tests, the vehicle failed to stop, from an initial speed of 20 miles per hour, before striking the pedestrian dummy. The testing was performed during daylight hours with adult pedestrian dummies. The tested vehicle performed worse at higher speeds, under dark conditions, and with child dummies.

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Speed from Video – Captain Video’s Specialty


James R. Schmidt, Jr., BSME, Sr. Collision Reconstruction Engineer ::::

I’m a collision reconstruction engineer with over 23 years of experience in the field. I’m affectionately known in the office as Captain Video, given my love for the evaluation of vehicle speed and crash-related parameters from surveillance videos.

Basic evaluation from stationary camera:

A 2019 Toyota Sienna minivan passes in front of a stopped dash cam. Speed from video is evaluated therefrom. Speed is distance over time. The easiest way to perform the evaluation is to look at the timeframe required to travel the vehicle’s wheelbase (i.e. the distance from the front wheel or axle to the rear wheel or axle). So, in this example, the minivan travels its 119 inch wheelbase in 7 frames of a 30 frame-per-second video. Distance is 119 inches, or 9.92 feet. Time is 7 frames divided by 30 frames per second, or 0.233 seconds. Calculating speed … 9.92 feet divided by 0.233 seconds is 42.5 feet per second, or ~29 mph. FYI, this was a 35mph speed limit roadway.

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Was it Road Rage? Can an Engineering Analysis Answer That Question?


Video

Justin P. Schorr, Ph.D, Principal Collision Reconstruction / Transportation Engineer ::::

A collision occurred when a school bus moved from the right lane of a limited access highway onto the rightside shoulder and contacted a disabled vehicle. It was dark and the disabled vehicle on the shoulder was not illuminated. The operator of the school bus testified that a tow truck located in the lane to his left executed a lane change, forcing him off the roadway and onto the shoulder into the disabled vehicle. The operator of the tow truck testified that the disabled vehicle was his intended “pickup,” but as he went to move from the center lane to the right lane to access the disabled vehicle, the school bus was trying to squeeze by him by passing him on the right, resulting in the collision.

Two forms of event data were available for analysis – video from the tow truck and engine control module data from both the tow truck and the bus. This data allowed for an accurate plotting of the speed of both vehicles prior to and at the time of the incident. Since the vehicles occupied the same place at the same time during the collision (i.e. the tow truck was touching the bus), the event data could be correlated such that their relative positions leading up to the collision could be plotted to scale. The video data also included a rearview camera making it so the position of the bus in the right lane as it approached the tow truck (which was initially in the center lane) could be seen. This data confirmed the independent correlation and plotting of the speed data from each vehicle.

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Inattentional Blindness


Motorcycle Blindness

Robert T. Lynch, PE, Senior Collision Reconstruction Engineer ::::

A person’s failure to notice an unexpected object located in plain sight is known as inattentional blindness. This phenomenon, rooted in the way the human brain processes (or fails to process) information, provides a framework to understand the looked-but-failed-to-see (LBFTS) crashes commonly associated with motorcycle collisions. LBFTS crashes are particularly troublesome because, despite clear conditions and the lack of other hazards or distractions, drivers will look in the direction of the oncoming motorcycle but still pull into its path. The brain must deal with a huge amount of sensory information during the driving task and cannot attend to everything due to the limitations of time and cognitive resources. The brain needs to decide what information is most important. The frequency of LBFTS crashes suggests that there is a connection with how the brain filters out information as motorcycles fall lower on the priority list for driving.

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Following Too Closely – Not Always as Straightforward as it May Seem


Following too close

Robert T. Lynch, PE, Senior Collision Reconstruction Engineer ::::

All states have a provision within their respective Vehicle Code pertaining to “following too closely” which states, in general, that “the driver of a motor vehicle shall not follow another vehicle more closely than is reasonable and prudent, having due regard for the speed of the vehicles and the traffic upon and the condition of the highway.”(1) Whenever a rear-end impact occurs, the investigating police officer will typically list “following too closely” as a contributing factor; however, not all drivers that rear-end another vehicle are keeping an unsafe following distance (a.k.a. headway) or are following “more closely than is reasonable and prudent” having due regard for the speed of the vehicles on the highway.

Most states recommend a 3 to 4-second “following distance rule” within their driver’s manual. This rule generally provides for sufficient distance to bring a vehicle to a stop in most driving situations; however, the rule is not conducive for drivers on congested highways where keeping such a distance would allow other vehicles to “cut in line” and effectively reduce safety by increasing the number of potential vehicular conflicts. It is often argued that the following distance rule is rarely observed in practice. Support for this argument is found in the review of the attached Google Earth™ aerial image of I-95 in Philadelphia, PA which illustrates that the majority of drivers within this image are accepting a following distance of 100 feet or less, with an average time headway (assuming the vehicle are traveling at the 55-mph speed limit) of about 1 second. A headway equivalent to 1 second is consistent with published research data on “real world” typical time headways. (2) The acceptance of a reduced headway suggests that drivers are “reading the road” assessing the state of traffic as a whole and not just focusing on the vehicle directly in front of them.

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Paying Attention: Will an Alert Driver Avoid a Crash?


alert-driver-avoid-crash

Robert T. Lynch, PE, Senior Collision Reconstruction Engineer ::::

Possibly… but not necessarily. I recently visited the Miami, Florida area on vacation and encountered several of these signs on the highways in and around the city. The wording of the sign had me reflecting on my undergraduate logic class, literally learning about the P’s and Q’s of modus ponens (if P then Q) and modus tollens (if not Q then not P). By the rules of inference, if a statement is true, then so is its contra-positive. In other words, (if P then Q) is the same as (if not Q then not P).

Now that we all are up to speed with our P’s and Q’s, when the Miami sign is applied to the logic framework, the sign would read: if a driver is alert then a crash can be avoided. Accepting this statement as true indicates that its contra-positive is also true: if a collision occurs then the driver was not alert. While this statement makes logical sense, as drivers who are not paying attention are more susceptible to crash, not all collisions occur due to driver inattention.

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