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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 develop guidance for a bridge pier protection program that will allow state transportation agencies to conduct risk-based assessments of bridges located within highway interchanges. At a minimum, the program should consider each structure’s redundancy, continuity, and the distance of bridge pier columns from the edge of traveled ways. Additionally, consider traffic volumes, traffic type, and the percentage of commercial vehicles transporting bulk liquid hazardous materials in identifying and prioritizing initiatives for preventing vulnerable bridges at high-risk interchanges from collapsing if struck or otherwise damaged by a heavy vehicle.
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 there are two ongoing studies that address bridge pier design factors—one that is nearly complete, led by the Texas Department of Transportation, and another that should be completed by September 2015, funded through NCHRP. When the findings are available, the FHWA will work with AASHTO to update the Load and Resistance Factor Design and Construction Specifications to provide guidance to the states for a bridge pier protection program for bridges that are vulnerable to collapse if struck by a heavy vehicle. Pending issuance and dissemination of the updated guidance, Safety Recommendations H-11-16 and -17 are classified OPEN—ACCEPTABLE RESPONSE.
-From Victor M. Mendez, Administrator: There is work currently underway to address this recommendation. At this time, the Texas Department of Transportation is conducting a pooled study on the Load and Resistance Factor Design (LRFD) Pier Design requirements which should be complete in the near future. In addition, the National Cooperative Highway Research Program (NCHRP) is funding a study on "Guidelines for Design and Shielding of Bridge Piers" (NCHRP 12-90). Objectives for this research include the following: • Develop risk-based guidelines for determining when bridge piers should be designed for heavy truck impact or shielded with a truck barrier; • Identify the most appropriate impact conditions for use in designing pier protection based upon the traffic, geometric, and operating characteristics of the adjacent highway; • Develop barrier selection and placement guidelines for protecting bridge piers from heavy truck impacts; and • Quantify the risk of head slap on tall barriers and provide guidance for design of tall barriers to reduce the potential for head slap. Based on the current work plan for the study, we anticipate that NCHRP 12-90 will be complete, and results distributed, by September 2015.
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