NHTSA Engineering Analysis EA04025

THE SUBJECT VEHICLES ARE HEAVY DUTY PICKUP TRUCKS WITH DIESEL ENGINES AND AUTOMATIC TRANSMISSIONS COMMONLY USED FOR COMMERCIAL AND WORK PURPOSES.A COLUMN MOUNTED SHIFT LEVER IS USED FOR GEAR SELECTION AND AN ELECTRONIC PRNDL ON THE INSTRUMENT PANEL PROVIDES GEAR POSITION INFORMATION TO THE DRIVER.THE SUBJECT VEHICLES ARE ALSO EQUIPPED WITH A BRAKE-TRANSMISSION SHIFT INTERLOCK THAT PREVENTS THE SHIFT LEVER FROM BEING MOVED FROM THE PARK POSITION (WHEN THE ENGINE IS ON) UNLESS THE BRAKE PEDAL IS DEPRESSED AND AN IGNITION-SHIFT INTERLOCK THAT PREVENTS KEY REMOVAL UNLESS THE TRANSMISSION IS IN THE PARK POSITION.COMPLAINANTS GENERALLY REPORT THAT THE VEHICLE WAS BEING OPERATED IN A FORWARD GEAR AND BROUGHT TO A STOP THROUGH BRAKE APPLICATION ON ALEVEL SURFACE, AT WHICH TIME THE OPERATOR MOVED THE SHIFT LEVER TO ENGAGE THE PARK POSITION.THE OPERATOR THEN OPENED THE DRIVER SIDE DOOR AND, WITHOUT VERIFYING PARK ENGAGEMENT (E.G., PRNDL GEAR INDICATION), SECURING THE PARK BRAKE, OR TURNING THE ENGINE OFF, EXITED THE VEHICLE.INITIALLY, NO VEHICLE MOVEMENT WAS APPARENT, HOWEVER, A SHORT TIME LATER, TYPICALLY REPORTED AS 10 TO 30 SECONDS, THE VEHICLE MOVED REARWARD UNDER ENGINE POWER.THE INCIDENT OFTEN ENDED IN A VEHICLE CRASH, AND SOMETIMES INVOLVED SERIOUS INJURY.TWO FATALITIES ARE ALLEGED.ODI?S ANALYSIS OF TEST VEHICLES AND SOME INCIDENT VEHICLES FOUND NO EVIDENCE TO INDICATE THAT A SHIFT LEVER PROPERLY PLACED IN PARK COULD UNINTENTIONALLY (I.E., WITHOUT DRIVER INPUT) DISENGAGE FROM THAT POSITION.HOWEVER, ODI DID FIND THAT THE SHIFT LEVER COULD BE INADVERTENTLY PLACED, AND REMAIN AT REST, WITHIN AN INTERMEDIATE POSITION BETWEEN THE PARK AND REVERSE GEAR POSITIONS.WHEN PLACED IN SUCH AN INTERMEDIATE POSITION, THE VEHICLE CAN EXPERIENCE A DELAYED PRESSURIZATION OF THE REVERSE HYDRAULIC CIRCUIT THAT IS SUFFICIENT TO CAUSE THE VEHICLE TO ROLL REARWARD UNDER POWER.THE DELAY PERIOD ALLOWS SUFFICIENT TIME FOR OPERATORS TO EXIT THE STATIONARY VEHICLE WITHOUT PERCEIVING THAT THE SHIFT