|Car, Truck or SUV Traffic Accident
US Roadways have a wide variety of motor vehicle traffic. This makes for unique traffic accident reconstruction
scenarios involving, sometimes, distinctly different vehicles.
The FHWA Traffic Monitoring Guide (TMG) recommends classifying vehicles into 13 different categories based on
vehicle configuration. Class 13 heavy trucks can have seven or more axles and gross vehicle weight ratings (GVWRs)
of 33,001 pounds or more.
Small Class 1 motorcycles, can weigh as little as 400 - 500 pounds. Passenger cars, light trucks, and SUVs can have
GVWRs anywhere from a few thousand pounds up to 10,000 pounds.
The weight of colliding vehicles is an intricate part of accident reconstruction. Certain vehicle attributes, such as
momentum, are directly dependant on weight. Likewise, certain methodologies of crash reconstruction become
increasingly sensitive as the weights of colliding vehicles distance themselves.
And, not only do vehicle weights dramatically affect accident reconstruction, but vehicle equipment does as well.
Anti-lock brake systems (ABS), stability control, headlamp type, automotive suspension, wheel base and more can all
influence the dynamic interaction among vehicles during a collision.
For example, the friction value, sometime referred to as drag factor, of a sliding or skidding heavy truck can be
significantly less than the frictional value possessed by a passenger car sliding or skidding on the same surface. Our
accident reconstruction experts will provide relevant analysis of those vehicle characteristics that influenced a crash.
Accident reconstruction experts are generally most concerned with dynamic friction. Dynamic friction, also called
kinetic or sliding friction, is a measure of the force resisting motion between two sliding bodies. The friction caused
between a sliding tire and the underlying road surface is one type of dynamic friction.
The proper assessment and application of tire to roadway friction, sometimes referred to as the coefficient of friction,
is critical when an expert accident reconstructionist analyzes a collision. Vehicle ABS systems attempt to maximize
roadway friction by not allowing a vehicle's wheels to lock. In most cases, peak friction is actually reached just prior to
wheel lock-up. To view a graph of an ABS vs Skid test, please click here.
The Federal Highway Administration (FHWA)
Traffic Monitoring Guide (TMG) recommends
classifying vehicles into 13 different categories.
All States currently use this classification scheme
or some variation of it for classifying vehicles. To
read FHWA's TMG, please click here.
Because of the wide variety of vehicles on the
road today, the Illinois Department of
Transportation (IL DOT) tracks fatal accidents by
vehicle type. To view Illinois' 2004 - 2008 fatal
crash statistics by vehicle
type, please click here.
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results depend on a variety of factors unique to each case. The results of any investigation/reconstruction do not guarantee or predict a similar result in any future case undertaken by Crash Data
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