If Speed of a Vehicle Known, Can We Determine Forces on Occupants?

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MSI
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If Speed of a Vehicle Known, Can We Determine Forces on Occupants?

Post by MSI » Fri Mar 03, 2017 8:38 am

Q: (rcd via email) If we know the speed of the vehicle at the time of the accident , type of the vehicle(Toyota etc..) can we determine the estimated force on a patient or driver to determine the extent of injury after a car accident?

A: Speed of a vehicle generally does not tell you anything about possibility of an injury since a car at 100 mph can simply coast to a stop position. Impact Speed change or DeltaV is generally used to characterize the exposure in a collision event. It can also help determine the possibility of an injury in a collision.

NHTSA (CIREN and other projects) and other research organizations look at impact speed change in collisions vs occupant injuries to characterize and categorize the possible injuries which have occurred and therefore can occur at various impact types and DeltaV levels.

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MSI
Site Admin
Posts: 1146
Joined: Thu Jun 18, 2009 12:37 pm

Re: If Speed of a Vehicle Known, Can We Determine Forces on Occupants?

Post by MSI » Sun Mar 05, 2017 2:20 pm

Q: (rcd via email in response to prior) When you get a chance would you look at this link formula to see if in general we can calculate force on a driver after an accident: A: The use of a constant-force deceleration to represent crashing vehicles and stretching seat-belt harnesses is unreliable and it constitutes a misleading presentation. It is generally accepted that a vehicle collision is best modeled as a quarter sign wave. Also in the example a vehicle stops from 30 MPH in approximately 1 foot which exceeds the crush resistance of typical vehicles.
A few other observations:
  • The Non-stretching seat belt example would cause occupants to share vehicle deceleration
  • The No seatbelt example includes a stopping distance , d, or 0.2 feet?! is that an assumption of a non energy absorbing vehicle interior?
  • The Belt Stretches approximation includes a 1.5 foot stop. The 1 foot stop for the vehicle from a 30 MPH is unrealistic and therefore so is the 'stretching belt' example.
For some additional background on the proper modeling of vehicular crashes and occupants, please see our 2011 paper:
  • See the section on Cal2D which includes:
    • The CAL-2D model was created "in order to help improve understanding of the complex relationships of force-acceleration-time-position-velocity that occur in the impact and energy-absorbing cycle of automobile passenger restraint systems". The study was performed to provide guidance concerning "(1) fundamental differences in the results obtained by static and dynamic testing and (2) the possible need for dynamic acceptance testing of seat belts.
      One of the results of the study was the conclusion that "the use of a very short stopping distance in a dynamic cart test of lap belts can produce a distorted comparison of the strength (when belt loads are not measured) and the performance of webbing materials with different load-elongation characteristics.
it is also covered in our paper:
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