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On October 22, 2009, about 10:38 a.m. eastern daylight time, a 2006 Navistar International truck-tractor in combination with a 1994 Mississippi Tank Company MC331 specification cargo tank semitrailer (the combination unit), operated by AmeriGas Propane, L.P., and laden with 9,001 gallons of liquefied petroleum gas, rolled over on a connection ramp after exiting Interstate 69 (I-69) southbound to proceed south on Interstate 465 (I-465), about 10 miles northeast of downtown Indianapolis, Indiana. The truck driver was negotiating a left curve in the right lane on the connection ramp, which consisted of two southbound lanes, when the combination unit began to encroach upon the left lane, occupied by a 2007 Volvo S40 passenger car. The truck driver responded to the Volvo’s presence in the left lane by oversteering clockwise, causing the combination unit to veer to the right and travel onto the paved right shoulder. Moments later, the truck driver steered counterclockwise to redirect and return the combination unit from the right shoulder to the right lane. The truck driver’s excessive, rapid, evasive steering maneuver triggered a sequence of events that caused the cargo tank semitrailer to roll over, decouple from the truck-tractor, penetrate a steel W-beam guardrail, and collide with a bridge footing and concrete pier column supporting the southbound I-465 overpass. The collision entirely displaced the outside bridge pier column from its footing and resulted in a breach at the front of the cargo tank that allowed the liquefied petroleum gas to escape, form a vapor cloud, and ignite. The truck-tractor came to rest on its right side south of the I-465 overpasses, and the decoupled cargo tank semitrailer came to rest on its left side, near the bridge footing supporting the southbound I-465 overpass. The truck driver and the Volvo driver sustained serious injuries in the accident and postaccident fire, and three occupants of passenger vehicles traveling on I-465 received minor injuries from the postaccident fire. The National Transportation Safety Board (NTSB) determined that the probable cause of this accident was the excessive, rapid, evasive steering maneuver that the truck driver executed after the combination unit began to encroach upon the occupied left lane. Contributing to the rollover was the driver’s quickly steering the combination unit from the right shoulder to the right lane, the reduced cross slope of the paved right shoulder, and the susceptibility of the combination unit to rollover because of its high center of gravity. Mitigating the severity of the accident was the bridge design, including the elements of continuity and redundancy, which prevented the structure from collapsing. A basic requirement for evaluating the accident performance of U.S. Department of Transportation (DOT) specification cargo tanks (such as the MC331 involved in this accident) is access to data that can be used to quantify both the involvement of those tanks in reportable incidents and the in-service population of those same tanks. While the approximate number of DOT specification cargo tanks involved in accidents may be obtained from the Hazardous Materials Information System or other databases, there is limited access to accurate information on the population of cargo tanks by DOT specification. For example, the most precise number of petroleum-hauling DOT 406 cargo tank semitrailers cited in the Cargo Tank Roll Stability Study2 appeared to be somewhere between 10,648–60,003 units. When asked at the August 2010 NTSB public hearing, a Pipeline and Hazardous Materials Safety Administration (PHMSA) official acknowledged that the agency did not know the total number of cargo tanks by DOT specification that were currently in service.3 Further, PHMSA indicated that data analyses for evaluating the performance of DOT specification cargo tanks could be enhanced if the population of cargo tanks by DOT specification were available. The NTSB concludes that the absence of a requirement for motor carriers to periodically provide the number of cargo tanks by DOT specification limits the ability to perform accurate trend analyses. The limited information currently available for PHMSA to quantify the distribution of cargo tanks by DOT specification differs considerably, for example, from information that can be accessed by the Association of American Railroads (AAR) about tank cars used for transporting bulk liquids by rail. The AAR has used the Universal Machine Language Equipment Register (UMLER) equipment management information system as the industry’s central repository for registered railroad and intermodal equipment since 1968. The UMLER system is updated in real time and capable of tracking equipment status, ownership, and inspection history and providing the particular fleet profile.
TO THE FEDERAL HIGHWAY ADMINISTRATION: Work with the American Association of State Highway and Transportation Officials to evaluate vehicle design characteristics specific to the rollover thresholds of heavy trucks, including those having cargo tanks. Use the information obtained to develop best practices in highway design that will mitigate the increased rollover risk caused by reduced effective superelevation through changes in cross slope that high center of gravity commercial vehicles experience when they migrate onto the shoulder while negotiating curve sections of high-speed highways.
Original recommendation transmittal letter:
Open - Acceptable Response
Indianapolis, IN, United States
Rollover of a Truck-Tractor and Cargo Tank Semitrailer Carrying Liquified Petroleum Gas and Subsequent Fire
Addressee(s) and Addressee Status:
FHWA (Open - Acceptable Response)
Safety Recommendation History
The NTSB notes that the FHWA will propose a National Highway Cooperative Research Program (NCHRP) project, titled “Assessment and Updating of Horizontal Curve Design Criteria,” to work with AASHTO to develop the recommended best practices. Once the research findings are available, the FHWA will work with AASHTO and the Transportation Research Board to disseminate and codify the best-practice guidance. Pending further updates and issuance of the final guidance, Safety Recommendations H-11-13 and -14 are classified OPEN—ACCEPTABLE RESPONSE.
-From Victor M. Mendez, Administrator: Given the level of effort and resources required to address this recommendation, FHWA will work to propose a National Highway Cooperative Research Program (NCHRP) project to develop these best practices through the proposed project "Assessment and Updating of Horizontal Curve Design Criteria." The process for proposing and selecting NHCRP project is lengthy and would typically provide for completion for the work in spring 2016. Given the importance of this research, however, we will work with NCHRP and AASHTO to identify potential resources and process to substantially expedite this work. The FHWA will provide updates on any shortened timefrarne as additional information is available.
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