Seatback Strength

John R. Yannaccone, P.E., Sr. Mechanical Engineer
In 1966, the National Traffic and Motor Vehicle Safety Act established a set of safety standards for motor vehicles and established the National Highway Safety Bureau, now known as the National Highway Traffic Safety Administration (NHTSA). The Federal Motor Vehicle Safety Standard (FMVSS) 207, which focuses on the strength of vehicle seats, was among the standards established. FMVSS 207 includes a requirement for the strength of the seatback, which is tested by applying a rearward force near the top of the seatback and limits the post-test deformation after the seat is subjected to a specified moment or torque (a force applied at a distance). For decades, engineers have argued the FMVSS 207 requirements are inadequate for the safety of occupants in rear impacts.
When a vehicle is struck from behind, the seatback provides the primary means of restraint to the occupant. When the seatback deforms rearward, it can result in several issues. Once the seat reaches around 45° recline angle, it starts to lose the ability to retain the occupant and they begin to slide up the seatback. This can result in the occupant impacting the rear seat with their head or being ejected from under the seatbelt, exposing the occupant to a wide range of injuries. In addition to affecting the front seat occupants of the vehicle, this deformation of a seatback can expose backseat occupants to potential injuries. Continue reading “Seatback Strength”