“Properly designed energy absorbing (yielding) underride guard systems can provide the advantages of reduced accelerations and crush of the impacting vehicles, better control of crash energy dissipation, and lower loadings on the truck structure.”
(Lower loadings on the truck structure means the frame and support structures can withstand the forces generated at higher speeds prior to failure.)
“The test results also indicate that the loads imposed on an underride guard are reduced in off-center impacts as a result of less engagement of the full width of the striking vehicle and the tendency for the vehicle to spin out.”
(NHTSA fails to use this 1971 knowledge to render high-speed crashes survivable for offset crashes)
(Guard weight for properly braced stiff guard is much higher than for energy absorbing design, a government agency has lead us to believe this cannot be!) Guards were angled braced to near outside edges to increase strength in offset crashes. It was mentioned under stiff guards that guards exceeded strength of truck frames for crashes up to 40 mph. It is clear that lower loadings on the truck structure from energy-absorbing guards will allow protection in higher-speed crashes with reduced chance of failure of truck frames or attachment hardware. The angled bracing for the 1971 stiff guards exceeds the bracing from modern guards which have received awards from IIHS and The Truck Safety Coalition! These organizations gave safety awards to guard designs that were exceeded 48 years ago in safety design! These were 40 mph designs in 1971! How many people have died in the last 48 years that for lower cost could have been saved! These guards could have been produced and installed for very little cost difference from guards known to be ineffective in crashes. The philosophy of the trucking manufacturers was similar to the NRA (National Rifle Association) in that allowing any changes would start a cascading effect. These 40 mph guards either stiff or better energy-absorbing would have reduced insurance costs for the last 48 years. Saving a conservative 300 lives a year would have saved 15,000 lives! Why is this not mass murder and why have victims been cheated of any compensation!
1971 18″ Energy Absorbing Guard
“The two outboard support are angled to provide increased lateral stability to the system. The weight of this guard configuration was approximately 200 lbs.”
It was easier and cheaper to attach this guard 18 inches beyond the trailer, extending guards out a foot from the trailer can increase protection beyond 60 mph. In the next few years as we move to electric trucks the cost of operation of slightly heavier guards will be minimal, they will decrease range per charge rather than cost per mile. Extending these guards beyond the rear of the truck to increase stroke distance of the pistons might add up to 100 lbs to the guard weight.
18″ Energy Absorbing Guard
1971 18″ Rigid Guard
“The calculated weight of this guard and support structure is 340 lbs. Supporting structure for the bumper includes 3″ x 2″ x 1/4″ vertical tubes welded to the aft surface of the cargo platform and eight 3″ to 5.7″ #I beams angled forward and welded to the trailer frame and cargo bed side rails.”
18″ Rigid Guard with angled extra bracing