You hear it all the time in the medicolegal community,
minimal property damage so no personal injury. It was a low impact collision,
barely a scratch on the vehicle. Insurance adjusters typically consider
a "low impact" accident one in which there was little or no visible
physical damage to the vehicle. At best, there might be a dime-sized dent in
the bumper and the estimated cost of repair was under a hundred dollars. Over
the years insurance companies have expanded it to $100.00, $250.00, $500.00,
$1,000.00, to $2,000.00 and more. Basically, a “low impact collision” is
whatever the insurance company says it is, but that’s hardly the case. Whether a person was injured, in a "low
impact" accident is always a matter
of opinion the doctors, the lawyers and the patients.
The question of at what speed do you
get a soft-tissue injury has always been debated. It is complicated by human and physical variables,
which are difficult to define, and even more difficult to test. Here are some of the human and physical
variables that contribute soft tissue injuries.
·
Awareness of impending crash
·
Bracing for impact
·
Sex
·
Age
·
Position in Vehicle
·
Stature
Some of
the dynamic and vehicle factors that contribute to soft tissue injuries:
·
Vehicles involved
·
Speed differential
·
Vehicle weight
·
Location of impact
·
Direction of impact
·
Head restraint location
·
Seat failure
·
Seat back angle
·
Seat back height
"Low-speed"
impact refers to 1-2 miles per hour and goes up to 20-25 mph. "Moderate
speeds" are 25-40 mph and "high speeds" are 40 mph and over”1. In a study by Chapline et al the largest
category of injury crashes were graded as having no damage. In these, 38% of females and 19% of males had
symptoms. When damage was rated as
minor, these percentages were 54% and 34%.
This study demonstrates that injury occurs when there is no damage to
the vehicle. Brault JR et al used human
volunteer crash testing to produce injuries in 29% and 38% of the participants
in 2.5 m.p.h. and 5 m.p.h. “It
appears that the threshold for injury, even in adult healthy volunteers under
ideal laboratory conditions, may be as low as 2.5 mph”5.
There are many studies that
confirm low speed collisions with minimal damage to the vehicle cause injuryto
the operator and passengers. Research
quoted by White and Panjabe states that an eight mph rear-end
collision may result in a two g force acceleration of the impacted vehicle and
a five g force acceleration acting on the occupant's head within 250 msec of
impact. (One g equals an acceleration of approximately 32 ft./sec.) Car crashes
happen in literally a blink of an eye. The point is that the head and neck
experience more g forces than the car in low-speed impacts1. Research has shown
that high impact forces are transmitted directly to the occupant in low-speed
impacts and that the vehicle does not begin to crush until impact speed exceeds
15 or 20 mph.1 Bumpers are
made in a variety ways, ie. gas shock absorbers and polystyrene, able to withstand
8.1 to 12.4 m.p.h. resulting in less damage to the vehicle and more g force to
the occupants 7,8,9,10. Basically
vehicles of today are being built to withstand more impact, but humans are
not. It is a fact that low speed/impact
crashes cause personal injury to the occupants.
1. Jeffrey Tucker, DC, DACRB, Injury with Low-Speed Collisions, Dynamic Chiropractic May 22, 1995, Vol. 13, Issue 11.
2.
States JD, Balcerak
JD, Williams JS, et al.: Injury frequency and head restraint effectiveness in
rear end impact accidents. In Proceedings of 16th Stapp Car Crash Conference,
Detroit, MI, 228-257, 1972.
3. Chapline JF,
Ferguson SA, Lillis RP, Lund AK, William AF. Neck Pain and head restraint
position relative to the drivers head in rear-end collisions. Accident Analysis and Prevention 2000;
32:287-297.
4. Brault JR, Wheeler JB, Siegmund GP,
Brault EJ. Clinical response of human subjects to rear-end auto collisions.
Arch Phys Med Rehabil 79:72-80, 1998.
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