Characteristics of Trailer Rear Impact Guard - Interdependence of Guard Strength, Energy Absorption, Occupant Acceleration Forces and Passenger Compartment Intrusion

Document Type

Technical Paper

Publication Date


Publication Title

SAE International


FMVSS 223 and 224 set standards for “Rear Impact Protection” for trailers and semi-trailers with a gross weight rating greater than 10000 pounds. A limited amount of experimental data is available for evaluating the different performance attributes of rear impact guards. The crash tests are usually limited to fixed parameters such as impact speed, guard height, strength and energy absorption, etc. There also seems to be some misunderstanding of the interdependence of guard strength and energy absorption, and their combined effect on the guard’s ability to limit underride while keeping occupant acceleration forces in a safe range.

In this paper, we validated the Finite Element (FE) model of an existing rear impact guard against actual FMVSS 223 tests. We also modified a previously evaluated FE model of a 1990 Ford Taurus by updating its hood geometry and material properties. Finally, through a series of simulations, we provided insight into the interaction between guard strength, guard energy absorption, Passenger Compartment Intrusion (PCI) and the acceleration forces potentially experienced by a vehicle occupant. Performance characteristics such as strength and energy absorption were evaluated for impact speeds ranging from 25 to 50 mph involving four guard strength levels, namely a rigid guard, a minimally compliant guard, and two compliant guards with twice and thrice the strength specified in FMVSS 223.






SAE World Congress & Exhibition. Detroit, MichiganApril 14-17, 2008


© 2008 SAE International. All rights reserved.