Maybe you have noticed as you pass a semi truck that, due to its high ground clearance, your shoulders are about level with the bottom of the trailer. At the back of the truck, there is a bar that hangs down to about the front bumper of your car, and unless you hit it going very fast, it will catch your car so that the crumple zones and airbag activate.
If the tractor trailer jackknifed and you ran into the side, there would be no such safety mechanism. Crash tests by the Insurance Institute for Highway Safety show that the bottom of the trailer would shear the windshield and roof of a midsize sedan off the vehicle. Most people in passenger vehicles in this situation are decapitated.
The IIHS is not the only safety agency that has noted this hazard. The National Highway Traffic Safety Administration has investigated hundreds of underride accidents, and the agency's safety experts believe that some method for preventing these devastating crashes is necessary. It has not yet endorsed the side underride guards that are currently available on the market.
However, members of the U.S. Senate believe it is time to require underride guards. If Congress passes the Stop Underrides Act of 2017, all tractor trailers will have to have the guards, not only on the back and sides of the trailer but also on the front of the truck.
The bill is a bipartisan effort to stop the preventable fatalities that typically occur in underride crashes. Senators introduced the bill last December, and it is currently before the Committee on Commerce, Science, and Transportation. If Congress enacts the law, you will not immediately begin seeing the improved and additional guards on trailers. The bill states that new tractor trailers must have the guards within one year of the legislation's publication. Companies and owners with trucks already on the road will have two years to retrofit their vehicles to meet the standards.