sentences:  The U.S. National Transportation Safety Board (NTSB) dispatched a team to the scene and began an investigation.Local and state police and officials of the Georgia Department of Transportation (GDOT) also investigated.In its final report, the NTSB determined that the probable cause was "the motorcoach driver's mistaking the HOV-only left exit ramp to Northside Drive for the southbound Interstate 75 HOV through lane."