A Summary of the Hurt Study
Findings from the Hurt Study
Motorcycle Accident Cause Factors and Identification of Countermeasures
A motorcycle accident study offers you and your students a wealth of
information about accidents and how to avoid them. The "Motorcycle
Accident Cause Factors and Identification of Countermeasures," is a study
conducted by the University of Southern California (USC). With funds from
the National Highway Traffic Safety Administration, researcher Harry Hurt
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.
Reprinted here for your information and use are the findings.
The final report is several hundred pages. If you choose to have this
document in your resource library, the order information is:
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,
This document is available through:
California 90007, Contract No. DOT HS-5-01160, January 1981 (Final Report)
The National Technical Information Service, Springfield, Virginia 22161
"Motorcycle Accident Cause Factors and Identification of Countermeasures"
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
- 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
- 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
- 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
- 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
- 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
- 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.
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Last Update: Monday, September 18, 2005