SAFETY MEASURES: SUSPENSIONS AND STABILITY CONTROL
The National Highway Traffic Safety Administration (NHTSA) today amended Federal Motor Vehicle Safety Standard No 136 which was first established in June of this year. The standard is designed to ensure compliance of heavy truck tractors and large buses with new rules regarding Electronic Stability Control (ESC), hoping to reduce untripped rollovers and mitigate severe oversteer and understeer conditions which lead to loss of control.
In a 2011 research note, the NHTSA found, based on the agency’s estimates regarding the effectiveness of ESC systems, the rule will prevent 1,424 to 1,759 crashes per year resulting in 505 to 649 injuries and 40 to 49 fatalities. They determined that ESC systems can be 40 to 56 percent effective in reducing first-event untripped rollovers and 14 percent effective in eliminating loss-of-control crashes caused by severe oversteer or understeer conditions.
It is worth mentioning that this rule only affects truck tractors and large buses of a certain size. All new typical three-axle truck tractors manufactured on or after August 1, 2017 must have an ESC system, and it will be required for all other truck tractors by end of 2019. These include two-axle vehicles, which have been more recently required to satisfy new, reduced minimum stopping distance requirements, and severe-service tractors.
Here at Hyliion, we’re developing ESC inside the SMART suspension system adding an additional layer of protection against untripped rollovers and loss-of-control crashes caused by severe oversteer and understeer conditions. More study is required to understand the role of trailer yaw in trucking accidents, but the metrics cited by NHTSA imply great gains to be had while controlling stability from the rear in addition to the front.
The final rule should be highly cost effective and beneficial. NHTSA estimates net benefits between $412 and $525 million at the 3 percent discount rate and $312 to $401 million at the 7 percent discount rate. The benefits stem from prevented crashes, reduced congestion, and prevention of property damage. Check out the cost benefit analysis below, or visit the Office of the Federal Register to read the provisions of the rule in full.
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