Whether large trucks are becoming less hazardous or not depends on which crash death rates you look at. Trucking industry officials say the trend is positive, pointing out that large truck crash death rates per mile traveled have come down. This fact has attracted some attention in light of recent regulatory proposals that would, among other things, change the hours truckers would be allowed to drive (see "Truck safety in the balance as hours of service are considered," October 21, 2000). But the decline in the per-mile death rate doesn't tell the whole story.
"Different pictures of truck safety emerge depending on what measures you use," says Institute researcher Stephen Lyman. "Truck safety has improved, but not in all respects, and more can be done."
A new Institute study takes stock of U.S. trends, using a range of indicators to examine deaths in large truck crashes during 1975-99. Occupant death rates were calculated per capita, per licensed driver, per registered truck, and per mile driven.
What emerges is that the overall public health burden of large truck crashes hasn't improved since 1975. In 1999, 4,663 passenger vehicle and large truck occupants died in large truck crashes — a rate of 1.71 per 100,000 population. Back in 1975, the toll was 3,673 occupant deaths at a rate of 1.70 per 100,000.
The trucking industry points to a different measure. Total truck mileage has increased almost 150 percent since 1975. More trucks are on the road. Yet overall occupant deaths per mile traveled have dropped almost 50 percent. In other words, for every mile driven by a truck half as many people are dying in truck crashes.
"It's because of the rise in mileage that the public health burden of large truck crashes hasn't lessened, even though deaths per mile have dropped," Lyman says.
The decline in per-mile death rates in large truck crashes has been greater among truck occupants. "To the extent that overall truck safety has improved, passenger vehicle occupants haven't benefited as much," Lyman says. Truck occupant death rates per mile fell 67 percent between 1975 and 1999. Among passenger vehicle occupants, the death rate in large truck crashes fell less — 43 percent.
The problem is the physics involved when a passenger vehicle collides with a large truck. The occupants of the smaller, lighter vehicle have far less chance of surviving. In two-vehicle crashes involving a large truck and a passenger vehicle, 98 percent of the deaths occur among passenger vehicle occupants.
"More could be done to protect truck drivers as well as the people who are sharing the road with them," Lyman says. "Potential countermeasures include changing large trucks by modifying the front ends to make them more compatible with passenger vehicles. We also need measures that are focused on drivers of both cars and trucks to, for example, increase safety belt use, reduce fatigue among truck drivers, and reduce alcohol involvement among the passenger vehicle drivers."
Two views about whether the safety of large trucks is improving
Per mile: Deaths in large truck crashes per 100 million truck miles
Measured per mile, occupant deaths in large truck crashes are decreasing (above). But when deaths are measured per capita (below), truck crash deaths aren't any less of a problem now than 25 years ago. In either case (per mile or per capita), the burden is greatest for passenger vehicle occupants in crashes with large trucks.
Per capita: Deaths in large truck crashes per 100,000 population