How the accident occurs: Tractor trailers usually stand 45 inches above the ground whereas small cars generally stand somewhere between 30-35 inches above the ground. If a car is traveling too closely when a tractor trailer stops, they could easily slide into the undercarriage of the trailer. The US Department of Transportation has made it a requirement that all trailers now come equipped with a rear bumper no taller than 22 inches. However, many bumpers will not withstand the force of a hard impact. This type of accident can also occur when a small vehicle slides into the undercarriage from the side of the tractor trailer. In almost all cases, this kind of accident is fatal as the entire top of the vehicle could be sliced away in the impact.
Maintain a safe driving distance. Tractor trailers need more time to slow down and may break sooner than a small car. Leaving enough space between your car and the trailer is crucial to avoid a rear-end collision where an under-ride accident could take place.
Space out. Do not dirve directly to the side of a tractor trailer unless passing. A tractor trailer may need to swerve into your lane to avoid hitting something in the road or the car in front of them if they are driving to fast.
Depending on how this accident takes place, this type of accident could be the fault of the tractor trailer driver or the driver of the smaller vehicle. If the smaller vehicle is following too closely, they will almost always be at fault. If the tractor trailer swerves into an opposing lane, the driver of the tractor trailer will almost always be at fault. A jury or a judge will make the ultimate decision of who was at fault and whether there was any contributory negligence.