Off-Road Vehicle Accidents


Off-road vehicle use and available products for the consumers to use off-road has increased dramatically over the past several decades.  With the increased use, the number of accidents resulting in serious injuries and death to the users have also increased in alarming numbers.  Many of these accidents are not caused by the users of these vehicles, but instead, are caused by the defects that are inherent in some of these off-road vehicles.  

Off-road vehicles (such as ATVs, UTVs, side-by-sides, etc.) are three-wheel, four-wheel, five-wheel, or six wheel vehicles which are "designed" for off-road use on a variety of terrains.  They are manufactured to be operated on low pressure and high flotation tires.  These vehicles are being used primarily as recreational vehicles.  However, a number of models have been designated and used specifically for agricultural and/or other utility or commercial applications.  Wright, Johnson, Carpenter, and Nelson (1991) reported that in 1990, there were approximately three million ATVs in the United States and that approximately half of the ATVs were the three-wheel units.  The CPSC (1991) reported that from 1982 to December 1990, there were more than one-half million accidents on off-road vehicles which required hospital emergency room care for the injuries and more than 1500 of these accidents resulted in deaths.  Most of the current injuries and fatalities which are associated with off-road vehicles now involve a four-wheel vehicle.

The original ATV, as we know them today, was developed in Japan by Osamu Takeuchi in the late 1960's for the Honda Motor Company.  The original objective by Honda was to develop a small vehicle that could operate on snow and, thus, compete in the snowmobile market.  Mr. Takeuchi's initial attempts were unsuccessful until the development of the high flotation, low pressure tires which were being used on other vehicles in the United States.  Mr. Takeuchi tried these high flotation, low pressure tires on vehicles of various wheel arrangements using motorcycle components.  He tried three-, four-, and five-wheel arrangements and then decided that the three-wheel design configuration with no differential and no suspension worked the best.  This design was further developed and tested in Japan and Australia and then offered for sale in 1970 as a new product: The Honda US-90 ("utility" and "snow" machine with a 90 cc engine).

In 1988, the U.S. Department of Justice worked out with the ATV manufacturers an out of court settlement which stopped the importing and sales of the three-wheel ATVs.  However, this did not stop the manufacturing, importing and sales of the four-wheel ATVs and other off-road vehicles.  Accidents are still occurring on all types of these off-road vehicles and there is a need to understand how and why these accidents occur.

As Wright, Johnson, Carpenter, and Nelson (1991) reported, most off-road vehicle accidents can usually be categorized into three basic areas:
  1. Control, maneuverability, or steering problems.    
2. Stability or overturn accidents.
3. Hand, foot, or leg injuries.

Accidents involving control or steering problems on ATVs are brought about by the fact that most ATVs have no differentials (solid rear axles) and that some ATVs have little or no suspension other than the soft balloon tires on which they ride.  Wright and Carpenter (1987) and Wright, Johnson, Carpenter, and Nelson (1991) reported that the rolling resistance or motion resistance for ATVs varied both in a turning maneuver for machines without differentials and with the deflection or deformation of the tires.  It was found, however, that there was very little variance in the rolling resistance from one hard surface to another (grass, hard soils, asphalt, and concrete).  The rolling resistance or motion resistance of the ATVs with no differentials (solid rear axles) goes up by as much as 300% as the machine is put into a tight turn.  This phenomena acts as a braking mechanism which in some cases can precipitate a roll-over due to the instability in the machine.  Steering or maneuverability and control problems with off-road vehicles are sometimes not realized by the investigating officer when writing up an accident report.  In many cases, the officer incorrectly theorizes that the operator was being inattentive or was operating the machine at speeds faster than they really were going.

The physics and mathematics of off-road vehicles' stability problems (both longitudinal and the lateral) are discussed in detail in the papers by Wright and Carpenter (1987) and Wright, Johnson, Carpenter, and Nelson (1991). Most off-road vehicles are susceptible to lateral upset or instability (vehicle tipping or rolling or flipping over on its side).  A forward pitch roll accident is where the machine and rider(s) go forward and off to the side at the same time.  A forward pitch roll is a lateral instability problem.  Tests which have been run by the present author along with others usually show that eye witnesses perceive speeds of off-road vehicles to be greater than the actual speed at which the vehicle was being operated.  On some four-wheel off-road vehicles with an operator or with an operator and passenger(s), lateral upset can occur at speeds less than 10 mph (16 km/h).  Although the tires in most cases are not defective in themselves, the use of these high coefficient of friction tires on the off-road vehicle can be a design defect.  Wright and Carpenter (1987); Wright, Johnson, Carpenter, and Nelson (1991); and Holloway, Wilson and Drach (1989) have measured coefficients of friction for various off-road vehicle tires.  As mentioned, the off-road vehicle tire is a low pressure, high contact area tire having a deep tread pattern.  Construction of most of these tires is such that they will undergo extreme deflection when lateral and/or longitudinal forces are applied.  Some of these tires will hold, let go and re-grab the surface as the sidewalls of the tire flex under lateral and/or longitudinal loads.  Thus, the tire (especially the soft sidewall tire) will jump or gallop along as lateral and/or longitudinal forces are applied.  These tires have extremely high coefficients of friction which means that they hold the surface very well and do not skid or slide very easily.  These tires will tend to scuff the ground which sometimes can be misconstrued as skid marks.

As can be seen from the preceding discussions, many off-road vehicles have considerable maneuverability, control, or steering problems in addition to stability problems during operation.  Thus, it is very important that the design of these machines consider the safety and protection of the rider(s) using these machines.  The occupant protection system on some of the off-road vehicles are non-existent or inadequate.  Consideration also must be given to the protection of the vehicle riders' feet, hands, and legs.

The present author along with others have run tests on these off-road vehicles both with and without occupants to determine if the control problems and the upset speeds which have been calculated are, in fact, valid in the real world.  These tests have borne out the information reported above.  In addition, these and other tests that have been run give a benchmark for data concerning damage to vehicles at different speeds.  Obviously, the harder surfaces being contacted (trees, other vehicles, etc.) will cause more damage to the vehicles than contacting softer surfaces such as the ground.  As the speed increases, the amount of damage to the machine also increases.  Most people do not realize that the kinetic energy carried by a machine travelling at 28 mph is approximately twice the energy of the same machine travelling at 20 mph.  Again, it is according to what surfaces are being contacted, but significant damage can occur to an off-road vehicle travelling at speeds of less than 16 mph (25 km/h).

In the investigation and analysis of off-road vehicle accidents, it is important to recognize all of accident causation factors.  Operator error such as consumption of alcohol or risk taking are sometimes causation factors.  Sometimes operator error is the only and total cause of the accident.  However, operator error is not the cause of off-road vehicle accidents as often as it is reported or claimed.  The causation factors due to design defects discussed above also have to be considered when investigating and analyzing an off-road vehicle accident.

This article discusses issues of general interest and does not give any specific legal or business advice pertaining to any specific circumstances.  Before acting upon any of its information, you should obtain appropriate advice from a lawyer or other qualified professional.

This article may not be duplicated, altered, distributed, saved, incorporated into another document or website, or otherwise modified without the permission of TASA. Contact for any questions.
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