Large trucks weigh more than 10,000 pounds and can be either single-unit vehicles or combination vehicles consisting of a single-unit truck or tractor pulling one or more trailers. In most states, the maximum permitted length for a single trailer is 53 feet. Tractors pulling two 28-foot trailers are known as twins or western doubles. Trucks even bigger than western doubles are allowed to travel on some of the nation's roads. These trucks, called longer combination vehicles, either have three trailers or have at least two trailers, one of which is 29 feet or longer, or the tractor and two trailers have a combined weight exceeding 80,000 pounds.
Tractor-trailers are involved in more fatal crashes per unit of travel than passenger cars -- 2.6 compared with 1.7 per 100 million miles traveled in 2001 -- even though a much higher proportion of tractor-trailer miles are traveled on well-designed interstate highways.
About 5,000 people die each year in crashes involving large trucks. In fatal two-vehicle crashes involving passenger vehicles and large trucks, 98 percent of the deaths occur to the people in the passenger vehicles. Large trucks accounted for 3 percent of registered vehicles and 7 percent of vehicle miles traveled in 2001 but were involved in 12 percent of all passenger vehicle occupant deaths and in 22 percent of multiple-vehicle passenger vehicle occupant deaths in 2001.
Yes. Driver fatigue is associated with truck crashes. Research shows truck crash risk increases with driver hours behind the wheel. Crash risk is also higher between midnight and 6 a.m. The long hours truck drivers work cause sleep deprivation, circadian desynchronization, and fatigue. Research has found that truck drivers reporting hours-of-service violations also were 77 percent more likely to report having fallen asleep behind the wheel during the month before the interview.
Yes. Studies conducted in the United States, New Zealand, and Australia indicate that truck drivers in their 20s have a high rate of involvement in both fatal and nonfatal crashes.
Under federal hours-of-service regulations that took effect January 2004, interstate commercial drivers won't be allowed to drive more than 11 hours or drive after 14 hours on duty until they have had a 10-hour break. Drivers cannot drive after accruing 60 work hours during a 7-day period or 70 work hours during an 8-day period, but a "restart" provision will allow truckers to actually go for 17 hours in 7 days or 88 hours in 8 days.
Studies suggest that these work rules are commonly violated. A 1990 study by the Insurance Institute for Automotive Safety estimated that, on a 1,200-mile route from Washington State to Minnesota, more than half of the tractor-trailer drivers violated hours-of-service regulations. When the Institute surveyed long-haul tractor-trailer drivers in four states in 1991, almost three-fourths of the respondents indicated they violated hours-of-service regulations. About one-third of them said they routinely drove more than 60-70 hours. More than 25 percent reported working 100 hours or more per week, and 19 percent admitted to falling asleep at the wheel one or more times during the preceding month. More recent studies by other researchers confirm that hours-of-service violations by interstate truckers continue to be common. The long hours driven by many truckers can lead to the use and abuse of stimulants.
Current regulations allow drivers to use written logbooks of their hours, which truck drivers call "comic books" because they are so easily falsified. Onboard computers reduce the opportunities for violating the rules because they automatically record when a truck is driven and its speed. The Institute and five other organizations petitioned the Department of Transportation to require the installation and use of tamper-resistant electronic onboard computers on commercial vehicles whose drivers now are required to maintain written logbooks. The National Transportation Safety Board also has repeatedly recommended that such recorders be mandated. In 2000, FMCSA published a proposal to require these devices but dropped the proposal from the final work-hour rules that take effect January 2004. This proposal has met with a lot of opposition from some members of the trucking industry, but some trucking associations have endorsed a requirement for electronic recorders.
Yes. The high center of gravity of large trucks increases their risk of rolling over, particularly on curving ramps. About half of deaths among occupants of large trucks occur in crashes in which their vehicle rolled over, compared with about 60 percent of SUV occupant deaths and 40 percent of pickup occupant deaths (both SUVs and pickups have high centers of gravity). In contrast, about 20 percent of passenger car occupant deaths occurred in vehicles that rolled over.
Yes. Institute researchers who examined crashes of large trucks in Washington State found that tractor-trailers with defective equipment were twice as likely to be in crashes as trucks without defects. Brake defects were most common. They were found in 56 percent of the tractor-trailers involved in crashes. Steering equipment defects were found in 21 percent of crash-involved trucks.
Compared with passenger vehicles, stopping distances for trucks are much longer. On wet and slippery roads there are greater disparities between the braking capabilities of large trucks and cars. Current brake problems are aggravated by the poor maintenance practices of some truck companies. Out-of-adjustment brakes are the most common reason for authorities to order trucks out of service.
In an under ride crash, a passenger vehicle goes partially or wholly under a truck or trailer, increasing the likelihood of death or serious injury to the passenger vehicle occupants. The problem of fatal under ride crashes has been substantially underestimated by NHTSA, according to Institute research. A 1997 Institute study of fatal crashes between large trucks and cars estimates that front, rear, or side under ride occurred in half of these crashes.
During the day, trucks are easy to see, but it's a different story at night. Research indicates that if drivers of other vehicles can recognize medium and heavy trucks more easily, they can gauge their speed and distance more accurately and respond sooner when necessary. Federal studies have reported that enhancing the conspicuity of trailers reduced the incidence of crashes in which trailers were hit from the side or rear at night on unlighted roads. A federal rule requires improved conspicuity -- adding reflective sheeting or reflectors -- for trailers manufactured after December 1993 and truck tractors (bobtails) manufactured after July 1, 1997. Starting June 1, 2001, the Department of Transportation required the enhanced markings for all trailers on the road, not just new ones.