Tests show that big-rig bumpers pose risks to cars in certain crashes

Big-rig trailers are required to have underride guards on the back, essentially "bumpers" to prevent cars from running beneath the trailer in a collision. Through rigorous testing, the Insurance Institute for Highway Safety (IIHS) has found that significant risks still exist for passenger-car drivers.

The IIHS has found that some guards appear engineered for minimal compliance and may present a mortal threat to drivers, most especially in an impact where just the corner of the guard is struck.

When designed to withstand an impact, these bumpers allow an automobile's crash structure to deform, absorb energy, and protect occupants. Should the bumper fold forward, or the corner bend away, the car may go under the trailer, with the cargo box striking the car roof leading to a tragic outcome. (Check out the video below for a dramatic demonstration.)

IIHS petitioned the National Highway Traffic Safety Administration back in 2011, calling for tougher standards. While no formal action followed, IIHS reports that they are seeing real-world improvements thanks to a tougher Canadian standard.

Among 2,241 passenger vehicle occupants killed in large truck crashes in 2011, IIHS attributes 260 fatalities to accidents involving passenger cars rear-ending a semi-tractor trailer. While there has been a notable decline, IIHS attributes changes in traffic volume due to the challenged economy as a key factor. Accident specifics can be difficult to track, but the IIHS found in a study of 115 such crashes, only about one-fifth involved no underride or negligible underride.

Recent crash tests conducted by the Institute note progress, with good results among the eight top-selling trailers for full-width and 50-percent overlap impacts, in almost all cases. However, the 30-percent overlap test (the minimum overlap where the passenger vehicle occupant's head is likely to strike the trailer) found that most evaluated trailers failed.

The takeway is that the IIHS feels the Canadian standard marks an improvement over U.S. requirements, but more can be done. The IIHS continues to ask NHTSA to develop more stringent regulations and hopes that the industry voluntarily makes improvements in the meantime.

Consumers Union continues to support the IIHS position and hopes the government safety agency will consider these latest findings as it looks for ways to further reduce highway deaths and injuries.

—Jeff Bartlett