On October 22, 2009, about 10:38 am. 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 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. The truck driver's excessive, rapid, evasive steering maneuver to return the combination unit to the roadway 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-465overpass. 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. Major safety issues were identified in this investigation were cargo tank rollover prevention as they relate to highway and vehicle design. As a result of its investigation, the National Transportation Safety Board has issued safety recommendations to the U.S. Department of Transportation, Federal Motor Carrier Safety Administration, Pipeline and Hazardous Materials Safety Administration, National Highway Traffic Safety Administration, Federal Highway Administration, and American Association of State Highway and Transportation Officials.