Most fatal crashes involving heavy trucks are not the fault of truckers, U-M study says.

April 24, 2007
Contact: Bernie DeGroat bernied@umich.edu

ANN ARBOR—While public debate on the safety of
large, commercial trucks usually focuses on the driving
behaviors of truck drivers, such as fatigue and speeding,
truckers are not to blame for most fatal crashes involving
trucks and passenger vehicles, says a University of
Michigan researcher.

In a study of national crash data on fatal two-vehicle
accidents involving a heavy truck, Daniel F. Blower of the
U-M Transportation Research Institute (UMTRI) found that
the actions of drivers of passenger vehicles alone
contribute to 70 percent of the crashes. On the other
hand, truck drivers alone commit driving errors in 16
percent of the accidents, while both drivers make errors 10
percent of the time.

“Taken at face value, this seems to indicate that
passenger-vehicle drivers contribute disproportionately to
fatal crashes involving a truck and a passenger vehicle,”
says Blower, who notes that the purpose of his study is not
to assign blame, but to understand the full range of
actions that contribute to fatal truck accidents.

One explanation for the disparity, he says, could be
that since it is typically the driver of the passenger
vehicle who is killed in such fatal crashes—about 40
times more often than the truck driver—the deceased
driver obviously cannot give his or her side of what
happened.

But Blower says that the “surviving driver” hypothesis
is too simple. In crashes where both drivers survive, the
driver of the passenger vehicle is still the primary cause
more than twice as often as the truck driver.

Accident investigators, he says, have other sources of
information to determine what happened in a crash—beyond
deciding which driver’s story to believe.

“Physical evidence about what happened—who ran into
whom—is a powerful indicator and usually shows that the
driver of the passenger vehicle made the error that led to
the collision,” Blower says.

Using data from UMTRI and the National Highway
Transportation Safety Administration, Blower analyzed the
nearly 5,500 fatal accidents that involved one heavy truck
and one passenger vehicle (car, van, sport-utility vehicle,
pickup or light truck) in 1994 and 1995 (the most recent
years with complete crash data).

He found that the most common of all such crashes
passenger vehicle crosses the center line into the truck’s
path—eight times the rate of a truck crossing into the
lane of a passenger vehicle.

Further, Blower says, drivers of passenger vehicles
are six times more likely than truckers to sideswipe a
truck heading in the opposite direction, four times more
likely to hit a truck from behind and twice as likely to
turn across the path of a truck or sideswipe a truck going
in the same direction.

“The disproportion of passenger-vehicle driver errors
in fatal crashes may be in a sense related to the fact that
a fatality occurred, rather than that they are more
culpable,” he says. “Rear-end collisions provide the
clearest example, because a fatality is more likely to
occur if a passenger vehicle strikes the rear of a truck,
rather than the truck striking the rear of the passenger
vehicle.”

According to Blower, rear-end collisions caused by
passenger-vehicle drivers may occur because of driver
inattention, unsafe speed and truck conspicuity, while
harder-to-explain head-on crashes may be due to alcohol
use, night-time travel and weather.

“It is clear that addressing the ‘truck safety
problem’ must take into account more than just trucks and
truck drivers,” he says. “The actions of other vehicles on
the road contribute substantially to the toll. Even if all
trucks were operated perfectly, only a minority of the
fatal crashes would be eliminated.

“Truck crashes do not occur in isolation, but as part
of a larger system, involving the roadway and environment,
vehicle condition and the other vehicles in the traffic
system. If we want to reduce the toll of truck accidents,
we need to broaden our understanding beyond just trucks and
truck drivers.”