The vast size difference between 18 wheeler tractor trailers and standard cars and trucks, combined with key risk factors such as road conditions, the much longer stopping distances required for tractor-trailers, and truck driver fatigue, are pivotal hazards of these often fatal collisions.

The Insurance Institute for Highway Safety (IIHS) and the Highway Loss Data Institute reports that the majority of fatalities in large truck crashes are the occupants in other vehicles. Large trucks weigh up to 30 times as much as passenger vehicles and have far greater ground clearance, often resulting in standard size cars and trucks sliding beneath truck trailers, where they get trapped.

Though federal standards call for tractor-trailers to be equipped with underride guards as a safety mechanism to prevent that from happening, the IIHS finds that the guards can fail even in low-speed crashes. The IIHS is petitioning regulators to require underride guards that are strong enough to remain in place during a crash and to broaden rules to mandate guards for more large trucks and trailers, according to the agency’s website.

According to data from SafeRoads.org, large trucks are involved in multiple-vehicle fatal crashes at twice the rate of passenger vehicles, while nearly one in four passenger vehicle deaths in multiple-vehicle collisions involve a large truck.

Truck driver fatigue is a leading risk factor, according to SafeRoads, which reports that excessive daily and weekly work hours behind the wheel substantially increase the risk of crashes that result in death or serious injuries.

More than 750 people die and 20,000 people are injured each year as a direct result of fatigued commercial vehicle drivers, according to the Federal Motor Carrier Safety Administration (FMCSA), which is seeking to reduce the number of hours commercial drivers may operate a truck or bus.

Currently, drivers may operate a vehicle no more than 10 consecutive hours before a minimum eight-hour resting period. Under those guidelines, commercial drivers can spend 16 hours driving in any 24-hour period.

The proposed rule calls for a longer rest period with a rotating schedule of work and rest based on a 24-hour period instead of the current 18-hour one. It calls for drivers to work no more than 60 hours per week and to rest between nine and 12 continuous hours each day.

If interrupted by dispatchers, shippers or other personnel, the driver would be required to re-start the off-duty period, according to SafeRoads. Drivers would also be required to be off-duty for at least two nights after reaching the 60-hour work week threshold.

Electric On-Board Recorders (EOBR), which are tamper-proof, would monitor long-haul and regional drivers’ daily and weekly time behind the wheel. The IIHS states that many drivers violate regulations and drive longer than allowed. Electronic onboard recorders in commercial trucks would replace the handwritten logbooks kept by drivers that can be easily falsified.

Drivers injured or killed in 18 wheeler accidents, as well as family members, have to deal with medical expenses, lost wages, vehicle loss and funeral expenses.