Large trucks — semi-trucks in particular — are more likely to catch fire in higher speed vehicle crashes compared to light trucks and passenger vehicles, according to a recent study by the Kentucky Injury Prevention and Research Center (KIPRC).

In the study of Kentucky motor vehicle collisions between the 2000 and 2009, the large truck fire rate was 113% higher than the light truck/passenger car fire rate — 14% of vehicles that caught fire after a motor vehicle collision were large trucks. 

Although many of Kentucky’s 762 mi. of Interstate highway includes twists and curves, the study showed most large truck fires occurred on long stretches of straight highway, with a steady speed of at least 55 mph, and the majority of these large truck fires occurred in single-vehicle accidents involving only the truck and its driver. 

Dr. Terry Bunn, director of KIPRC, said larger vehicles’ weight may result in greater impact forces in collisions that may compromise vulnerable fuel tanks, and leaking fuel is more likely to ignite.

“Large trucks typically have two 150-gal. diesel fuel tanks on the tractor, and another 50-gal. fuel tank if the tractor is hauling a refrigerated trailer. Fuel tanks for large trucks have greater exposure and are much less protected than light trucks and passenger vehicles,” said Bunn.

Another source of vulnerability with large trucks is the crossover lines between the two fuel tanks, he said.  During impact, they may fail due to tear, rupture or puncture and increase the risk of fire. The lack of inertia fuel switches as standard equipment in large truck purchases may also increase the risk of collision fires, he said.

The study cites decreased vehicle stiffness and reduced crush space in the semi-truck cab as well as driver sleepiness and fatigue as additional causes of large truck fires. If a driver falls asleep and takes no evasive maneuvers to avoid fixed objects such as trees and bridge abutments, the driver is more likely to have a higher impact crash, Bunn said.

Bunn suggests the incidence of large truck fires can be reduced or eliminated by:

  • Mandatory inertia fuel switches
  • Company training on seatbelt safety
  • Rigid roadside barriers to contain and redirect semi-trucks from leaving the roadway
  • Crossover lines protection
  • Protected placement of fuel tanks
  • Enforcements of rest period and quality sleep for drivers
  • Investment in driver fatigue prevention technology
  • Elimination of cab distractions

In addition, “fire safety approaches based on input from truck drivers, trucking companies, large truck manufacturers, and roadway engineers are all needed to reduce large truck fires,” Bunn said.

Bunn’s study can be found at http://www.ncbi.nlm.nih.gov/pubmed/22405242.