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From:
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NTSB
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To:
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NHTSA
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Date:
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8/9/2012
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Response:
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Notation 8429: The National Transportation Safety Board (NTSB) has reviewed the National Highway Traffic Safety Administration's (NHTSA) Notice of Proposed Rulemaking to establish Federal Motor Vehicle Safety Standard (FMVSS) No. 136, Electronic Stability Control Systems for Heavy Vehicles, as published in Volume 77 of the Federal Register on May 23, 2012. The proposed rule would require truck tractors and certain buses with a gross vehicle weight rating (GVWR) over 26,000 pounds to be equipped with an electronic stability control (ESC) system meeting specified equipment and performance criteria.
The NTSB has long advocated the study and implementation of crash avoidance technologies, such as ESC, to assist drivers in maintaining control of commercial motor vehicles. As a result of our investigation of a multivehicle collision in Slinger, Wisconsin, in February 1997, the NTSB recommended that NHTSA conduct research to evaluate the benefits of adding traction control devices to antilock brake systems (H-98-9). Based on NHTSA research for the current rulemaking effort, the NTSB classified this recommendation "Closed-Acceptable Action" in January 2012. In the investigation of a seven-fatal mid-size bus rollover accident in Dolan Springs, Arizona, in January 2009, the NTSB addressed the benefits of equipping buses with a GVWR greater than 10,000 pounds with stability control systems and issued Safety Recommendations H -10-5 and -6 to NHTSA:
Develop stability control .system performance standard) applicahle to newly manufactured buses with a gross vehicle weight rating above 10, 000 pounds. (H-10-5)
Once the performance standards from Safety Recommendation H-10-5 have been developed, require the installation of stability control systems in all newly manufactured buses in which this technology could have a safety benefit. (H-10-6)
Upon completion of another commercial vehicle rollover accident investigation-in Indianapolis, Indiana, in October 2009, involving the rollover of a cargo tank trailer carrying liquefied petroleum gas and a subsequent fire3-the NTSB closed Safety Recommendations H-10-5 and -6 and issued superseding and broader Safety Recommendations H-11-7 and -8 to NHTSA:
Develop stability control system performance standards for all commercial motor vehicles and buses with a gross vehicle weight rating greater than 10, 000 pounds, regardless of whether the vehicles are equipped with a hydraulic or a pneumatic brake system. (H-11-7)
Once the performance standards from Safety Recommendation H-II-7 have been developed, require the installation of stability control systems on all newly manufactured commercial vehicles with a gross vehicle weight rating greater than 10, 000 pounds. (H-11-8)
In the Indianapolis investigation, the NTSB also concluded that a retrofit for stability control systems would be advantageous given the long service life of cargo tank trailers and the potential safety risks posed by the hazardous materials they typically transport. And, because roll stability control (RSC) systems do not require the same integrated sensors and communication systems as ESC, making them more feasible to install as a retrofit, the NTSB issued Safety Recommendation H-11-3 to the Federal Motor Carrier Safety Administration:
Require all in-use cargo tank trailers with a gross vehicle weight rating greater than 10, 000 pounds to be retrofitted with a rollover stability control system. (H-1l-3)
The proposed rule has assessed the benefits of ESC versus RSC systems, acknowledging that RSC systems lack the ability to affect the directional control of a vehicle in situations of potential rollover. The NTSB agrees with NHTSA that there are additional benefits of ESC over RSC and applauds the research and testing that NHTSA conducted to come to this conclusion. Although NHTSA found that RSC on trailers would save fewer than 10 lives per year and would not be cost beneficial, the NTSB stands by Safety Recommendation H-1l-3 for cargo tank trailers to be retrofitted with RSC systems due to the high potential they hold for catastrophic damage and loss of life in the event of a hazardous materials release.
The NTSB recognizes that FMVSS No.l26 requires ESC systems to be in place on light vehicles, and the proposed rulemaking extends the requirement for ESC systems to a large number of heavy vehicles. However, between the upper bounds of FMVSS No. 126, a GVWR of 10,000 pounds, and the lower bounds of the proposed FMVSS No.136, a GVWR of 26,000 pounds, there is a gap where stability control systems will not be required.
A vehicle type within this gap that is of particular interest to the NTSB is mid-size buses. The Dolan Springs bus, a mid-size bus with a GVWR of 19,500 pounds, would not be covered in the proposed ESC rulemaking. During its Dolan Springs investigation, the NTSB estimated that the production volume of mid-size buses was 11,600 units per year, on average. Mid-size buses, which are used to transport groups of 16-40 people, should be held to the same--if not higher standards than vehicles used to transport cargo. Mid-size buses also have higher centers of gravity than many other passenger-carrying vehicles, making them more prone to rollover, and therefore more likely to benefit from rollover prevention technologies.
The proposed rule also does not address ESC systems for other types of buses, and instead proposes exemptions for buses with fewer than 16 seating positions, buses with limited forward-facing seating configurations (such as limo-buses), urban transit buses, and school buses. We understand that certain exemptions to the rule may be required for slow-moving or specialty vehicles, but when it comes to vehicles that transport people, especially children, the NTSB encourages NHTSA to be as far-reaching as possible when implementing life-saving safety technologies such as ESC.
The proposed rule also excludes medium-duty and single-unit trucks, which could benefit from stability control systems. As pointed out in the proposed rulemaking, a safety benefit study applicable to such commercial vehicles is underway, and ESC systems are still in development for medium-duty trucks and buses equipped with hydraulic brakes. The NTSB is pleased to see that steps are underway to equip the largest populations within the commercial vehicle fleet with stability control systems without waiting for their availability on all types of vehicles, but we will continue to advocate that this safety technology be universal.
As recognized in the proposed rule, the NTSB has also issued safety recommendations on collision warning with active braking and adaptive cruise control systems, for which ESC systems are required as a baseline technology to enable vehicle braking without driver input. In 2001, the NTSB published a Special Investigation Report of nine rear-end accidents in which 20 people died and 181 were injured,5 and issued Safety Recommendations H-01-6 and -7 to NHTSA:
Complete rule making on adaptive cruise control and collision warning system performance standards for new commercial vehicles. At a minimum, these standards should address obstacle detection distance, timing of alerts, and human factors guidelines, such as the mode and type of warning. (H-01-6)
After promulgating performance standards for collision warning systems for commercial vehicles, require that all new commercial vehicles be equipped with a collision warning system. (H-Ol-7)
At the conclusion of the investigation of an October 2005 accident near Osseo, Wisconsin-involving the rollover of a truck-tractor semitrailer combination unit, which was subsequently struck by a motorcoach-in which 5 people died and 36 were injured,6 the NTSB reiterated Safety Recommendations H-0l-6 and -7 and issued Safety Recommendation H-08-15 to NHTSA:
Determine whether equipping commercial vehicles with collision warning systems with active braking and electronic stability control systems will reduce commercial vehicle accidents. If these technologies are determined to be effective in reducing accidents, require their use on commercial vehicles. (H-08-15)
We believe that the advancement of crash avoidance and mitigation technologies is dependent on equipping the entire commercial vehicle population with ESC. The NTSB understands that ESC alone cannot prevent all accidents and that conditions such as aggressive steering inputs, excessive speed, and shifting loads limit its effectiveness. For this reason, we encourage NHSTA to not only continue moving forward on accident prevention technologies, but also to develop rollover performance standards to ensure that the static rollover stability of commercial vehicles is considered and optimized in the design and manufacturing stages.
The NTSB appreciates the opportunity to comment on this notice. Although we are encouraged by the proposed rulemaking and its effect on a large population of commercial motor vehicles, our open safety recommendations to NHTSA with regard to stability control systems include all commercial motor vehicles and buses with a GVWR greater than 10,000 pounds. Well-designed technology can improve driver performance and overall highway safety, and we will continue to support the development and requirement of such systems until a universal level of safety is realized.
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