Tag Archives: Robert T. Lynch

The Importance of Event Data in Low Speed Collisions


Event Data Recorder

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

All model year 2013 and newer vehicles equipped with an event data recorder (EDR) that are sold in the United States need to adhere to the requirements set forth in 49 CFR Part 563 of the federal standards.

Part 563 establishes minimum requirements for an EDR. In particular, an EDR must record an event if the vehicle experiences a Delta-V (change in velocity) above 5 mph from any direction: front, rear or side. When a vehicle sees a Delta-V greater than 5 mph, the EDR will record 5 seconds of pre-crash speed, braking, and acceleration data, as well as severity data for the impact itself.

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Mississippi Moon


Moon

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

…won’t you keep on shinin’ on me

When evaluating nighttime collisions, a reconstructionist may choose to visit the accident location under similar conditions in order to observe the artificial light sources (i.e. street lights, nearby business lighting, traffic lights, etc.) to get a sense of what a driver could have seen leading up to a collision. Where a well-lit intersection could illuminate the roadway as if it had the appearance of daytime, a driver on a dark roadway may not have sufficient time and distance to perceive, react and avoid a dark-clothed pedestrian crossing the roadway.

While the historical moon data is researched and taken into consideration for a similar conditioned inspection, the moon is often not a factor in contributing to the overall useful illumination of the roadway. The definition of “useful” illumination is often taken to be an area of the roadway illuminated above 3.2 LUX, the dark limit of civil twilight (~30 minutes after sunset). Research has shown that beyond the limit of civil twilight, visual recognition functions deteriorate rapidly. The term “twilight envelope” has been coined to describe the useful extent of the vehicle headlight beam effecting a driver’s visibility at night.

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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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Two Collision Contributors, One Code Violator


motorcycle-accident-reconstruction-expert-witness

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

A motorcycle traveled across the double yellow centerline into the opposite travel lane on a rural, two-lane roadway in order to pass a farm tractor. When the tractor turned left at the intersection a collision occurred. DJS Associates was retained to evaluate the matter to determine the contributing factors that led to the subject incident. The incident would have clearly been avoided if the tractor operator hadn’t turned left or if the motorcyclist decided not to pass the tractor at the intersection. So, in general, the actions of both operators could be considered as contributory. However, a review of the (Pennsylvania) state statutes indicated that the actions of the motorcyclist were in violation of the vehicle code while the tractor operator’s actions were in compliance with the vehicle code

The vehicle code requires that a left-hand turn be completed from the left-most lane available, and that the driver of a vehicle intending to turn left at an intersection yield the right-of-way to any vehicle approaching from the opposite direction which is so close as to constitute a hazard. From an engineering perspective, the actions of the tractor operator to turn left at the intersection from the travel lane were in compliance with the vehicle code.

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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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Dukes of Hazzard Jump… In A Minivan


Stake_body_truck

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

A stake body pickup truck, towing a landscape trailer, was parked on the right shoulder of a two-lane roadway on a clear, sunny day. The lawnmowing equipment in both the bed of the truck and the trailer had been removed. There was no rear gate for the stake body, and the ramp to the trailer was down. Along came a minivan that drifted onto the shoulder of the roadway and hit the ramp square-on. Tire marks were observed on the wooden boards affixed to the sides of the trailer and stake body, showing the path the minivan took through the air. Scrape marks were also observed to the roof of the pickup truck where the underside of the minivan grazed the roof during its flight. Other than these minor markings, the pickup truck and trailer sustained no significant damage. The minivan landed in front of the pickup truck on the shoulder of the roadway, coming to rest on all four tires where it then caught fire. Fortunately, the occupants of the minivan were able to get out of the vehicle before sustaining further injury from the fire. The minivan sustained no significant crush damage.

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