The 1981 Hurt study
Motorcycle Accident Cause Factors and
Identification of Countermeasures:
Motorcycle Accident Cause Factors and Identification of Countermeasures,
Volume 1: Technical Report, Hurt, H.H., Ouellet, J.V. and Thom, D.R.,
Traffic Safety Center, University of Southern California, Los Angeles,
California 90007, Contract No. DOT HS-5-01160, January 1981 (Final Report)
The Hurt study, published in 1981, was a ground-breaking report on the causes and
effects of motorcycle accidents. Although almost 20 years old at this time, the study
still offers riders insight into the statistics regarding motorcycle accidents and
tips on safer riding. With funds from the National Highway Traffic Safety Administration,
researcher Harry Hurt (from which the study gets its common name) of the University
of Southern California, investigated almost every aspect of 900 motorcycle accidents
in the Los Angeles area. Additionally, Hurt and his staff analyzed 3,600 motorcycle
traffic accident reports in the same geographic area.
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Findings
Throughout the accident and exposure data there are special observations which
relate to accident and injury causation and characteristics of the motorcycle accidents
studied. These findings are summarized as follows:
Approximately three-fourths of these motorcycle accidents involved collision with
another vehicle, which was most usually a passenger automobile.
Approximately one-fourth of these motorcycle accidents were single vehicle accidents
involving the motorcycle colliding with the roadway or some fixed object in the environment.
Vehicle failure accounted for less than 3% of these motorcycle accidents, and most
of those were single vehicle accidents where control was lost due to a puncture flat.
In the single vehicle accidents, motorcycle rider error was present as the accident
precipitating factor in about two-thirds of the cases, with the typical error being
a slideout and fall due to overbraking or running wide on a curve due to excess speed
or under-cornering.
Roadway defects (pavement ridges, potholes, etc.) were the accident cause in 2% of
the accidents; animal involvement was 1% of the accidents.
In the multiple vehicle accidents, the driver of the other vehicle violated the motorcycle
right-of-way and caused the accident in two-thirds of those accidents.
The failure of motorists to detect and recognize motorcycles in traffic is the predominating
cause of motorcycle accidents. The driver of the other vehicle involved in collision
with the motorcycle did not see the motorcycle before the collision, or did not see
the motorcycle until too late to avoid the collision.
Deliberate hostile action by a motorist against a motorcycle rider is a rare accident
cause. The most frequent accident configuration is the motorcycle proceeding straight
then the automobile makes a left turn in front of the oncoming motorcycle.
Intersections are the most likely place for the motorcycle accident, with the other
vehicle violating the motorcycle right-of-way, and often violating traffic controls.
Weather is not a factor in 98% of motorcycle accidents.
Most motorcycle accidents involve a short trip associated with shopping, errands,
friends, entertainment or recreation, and the accident is likely to happen in a very
short time close to the trip origin.
The view of the motorcycle or the other vehicle involved in the accident is limited
by glare or obstructed by other vehicles in almost half of the multiple vehicle accidents.
Conspicuity of the motorcycle is a critical factor in the multiple vehicle accidents,
and accident involvement is significantly reduced by the use of motorcycle headlamps
(on in daylight) and the wearing of high visibility yellow, orange or bright red
jackets.
Fuel system leaks and spills were present in 62% of the motorcycle accidents in the
post-crash phase. This represents an undue hazard for fire.
The median pre-crash speed was 29.8 mph, and the median crash speed was 21.5 mph,
and the one-in-a-thousand crash speed is approximately 86 mph.
The typical motorcycle pre-crash lines-of-sight to the traffic hazard portray no
contribution of the limits of peripheral vision; more than three-fourths of all accident
hazards are within 45deg of either side of straight ahead.
Conspicuity of the motorcycle is most critical for the frontal surfaces of the motorcycle
and rider.
Vehicle defects related to accident causation are rare and likely to be due to deficient
or defective maintenance.
Motorcycle riders between the ages of 16 and 24 are significantly overrepresented
in accidents; motorcycle riders between the ages of 30 and 50 are significantly underrepresented.
Although the majority of the accident-involved motorcycle riders are male (96%),
the female motorcycles riders are significantly overrepresented in the accident data.
Craftsmen, laborers, and students comprise most of the accident-involved motorcycle
riders. Professionals, sales workers, and craftsmen are underrepresented and laborers,
students and unemployed are overrepresented in the accidents.
Motorcycle riders with previous recent traffic citations and accidents are overrepresented
in the accident data.
The motorcycle riders involved in accidents are essentially without training; 92%
were self-taught or learned from family or friends. Motorcycle rider training experience
reduces accident involvement and is related to reduced injuries in the event of accidents.
More than half of the accident-involved motorcycle riders had less than 5 months
experience on the accident motorcycle, although the total street riding experience
was almost 3 years. Motorcycle riders with dirt bike experience are significantly
underrepresented in the accident data.
Lack of attention to the driving task is a common factor for the motorcyclist in
an accident.
Almost half of the fatal accidents show alcohol involvement.
Motorcycle riders in these accidents showed significant collision avoidance problems.
Most riders would overbrake and skid the rear wheel, and underbrake the front wheel
greatly reducing collision avoidance deceleration. The ability to countersteer and
swerve was essentially absent.
The typical motorcycle accident allows the motorcyclist just less than 2 seconds
to complete all collision avoidance action.
Passenger-carrying motorcycles are not overrepresented in the accident area.
The driver of the other vehicles involved in collision with the motorcycle are not
distinguished from other accident populations except that the ages of 20 to 29, and
beyond 65 are overrepresented. Also, these drivers are generally unfamiliar with
motorcycles.
The large displacement motorcycles are underrepresented in accidents but they are
associated with higher injury severity when involved in accidents.
Any effect of motorcycle color on accident involvement is not determinable from these
data, but is expected to be insignificant because the frontal surfaces are most often
presented to the other vehicle involved in the collision.
Motorcycles equipped with fairings and windshields are underrepresented in accidents,
most likely because of the contribution to conspicuity and the association with more
experienced and trained riders.
Motorcycle riders in these accidents were significantly without motorcycle license,
without any license, or with license revoked.
Motorcycle modifications such as those associated with the semi-chopper or cafe racer
are definitely overrepresented in accidents.
The likelihood of injury is extremely high in these motorcycle accidents-98% of the
multiple vehicle collisions and 96% of the single vehicle accidents resulted in some
kind of injury to the motorcycle rider; 45% resulted in more than a minor injury.
Half of the injuries to the somatic regions were to the ankle-foot, lower leg, knee,
and thigh-upper leg.
Crash bars are not an effective injury countermeasure; the reduction of injury to
the ankle-foot is balanced by increase of injury to the thigh-upper leg, knee, and
lower leg.
The use of heavy boots, jacket, gloves, etc., is effective in preventing or reducing
abrasions and lacerations, which are frequent but rarely severe injuries.
Groin injuries were sustained by the motorcyclist in at least 13% of the accidents,
which typified by multiple vehicle collision in frontal impact at higher than average
speed.
Injury severity increases with speed, alcohol involvement and motorcycle size.
Seventy-three percent of the accident-involved motorcycle riders used no eye protection,
and it is likely that the wind on the unprotected eyes contributed in impairment
of vision which delayed hazard detection.
Approximately 50% of the motorcycle riders in traffic were using safety helmets but
only 40% of the accident-involved motorcycle riders were wearing helmets at the time
of the accident.
Voluntary safety helmet use by those accident-involved motorcycle riders was lowest
for untrained, uneducated, young motorcycle riders on hot days and short trips.
The most deadly injuries to the accident victims were injuries to the chest and head.
The use of the safety helmet is the single critical factor in the prevention of reduction
of head injury; the safety helmet which complies with FMVSS 218 is a significantly
effective injury countermeasure.
Safety helmet use caused no attenuation of critical traffic sounds, no limitation
of precrash visual field, and no fatigue or loss of attention; no element of accident
causation was related to helmet use.
FMVSS 218 provides a high level of protection in traffic accidents, and needs modification
only to increase coverage at the back of the head and demonstrate impact protection
of the front of full facial coverage helmets, and insure all adult sizes for traffic
use are covered by the standard.
Helmeted riders and passengers showed significantly lower head and neck injury for
all types of injury, at all levels of injury severity.
The increased coverage of the full facial coverage helmet increases protection, and
significantly reduces face injuries.
There is not liability for neck injury by wearing a safety helmet; helmeted riders
had less neck injuries than unhelmeted riders. Only four minor injuries were attributable
to helmet use, and in each case the helmet prevented possible critical or fatal head
injury.
Sixty percent of the motorcyclists were not wearing safety helmets at the time of
the accident. Of this group, 26% said they did not wear helmets because they were
uncomfortable and inconvenient, and 53% simply had no expectation of accident involvement.
Valid motorcycle exposure data can be obtained only from collection at the traffic
site. Motor vehicle or driver license data presents information which is completely
unrelated to actual use.
Less than 10% of the motorcycle riders involved in these accidents had insurance
of any kind to provide medical care or replace property. Please note: the Hurt study
is one of several studies used by legislators in support of "helmet laws"
requiring helmet use by motorcyclists. A complete non-summarized version of this
document is available through: The National Technical Information Service, Springfield,
Virginia 22161 