I AM A RURAL MAIL CARRIER WITH WELL OVER 350,000 MILES DRIVEN ON MY ROUTE WITHOUT INCIDENT. I DRIVE IN ALL ROAD CONDITIONS ON GRAVEL AND PAVED ROADS. I WAS DRIVING MY 2006 PRIUS ON A WET BUT NOT MUDDY GRAVEL ROAD AT ABOUT 38 MPH. THE BACK END BEGAN TO SLIDE A LITTLE. I LET UP ON THE GAS WITH NO RESPONSE. I PRESSED THE BRAKE PEDAL WITH NO RESPONSE. I WENT INTO A DEEP DITCH FILLED WITH 3 FT TALL GRASS. I STEERED TO DRIVE THE CENTER OF THE DITCH AND CONTINUED WITH THE BRAKE FULLY DEPRESSED FOR ABOUT 15-20 FT, RIPPING THE TALL GRASS OUT BY THE ROOT AS I WENT. THE CAR TRAVELED OVER A DRIVEWAY APPROACH, STILL AT 35 MPH, STRIKING THE APPROACH WITH THE LEFT FRONT CORNER WITH ENOUGH FORCE TO BEND THE FRAME AND DO OTHER SERIOUS DAMAGE, BUT WITH NO AIRBAG DEPLOYMENT. I CONTINUED OVER THE APPROACH AND DOWN THE DITCH, STILL AT 35 MPH, FOR ANOTHER 30 OR MORE FEET. I WAS PRESSING AND HOLDING THE BRAKE AND LIFTING THE GAS PEDAL WITH MY TOE. THE GAS PEDAL WAS NOT STUCK AND THE ENGINE'S RPMS WERE LOW. ONLY WHEN I PUT THE CAR IN NEUTRAL DID IT SLOW TO STOP. IT TOOK SEVERAL ATTEMPTS TO GET THE CAR OUT OF THIS DITCH AS THE TRACTION CONTROL KEPT LURCHING AND STALLING. I WAS ABLE TO DRIVE THE CAR OUT AND HOME WITHOUT INCIDENT. IT HAD TO BE TOWED TO A DEALERSHIP FOR OVER $4000 IN REPAIRS. THIS WAS IN MID-2008 AND I DON'T KNOW IF ANY CORRECTIONS MADE OR WERE EVEN KNOWN AT THAT TIME. THIS WAS AN ABSOLUTELY TERRIFYING SITUATION. THE CAR DID NOT RESPOND TO ANY ACTION I TOOK. I HAD NO C