THE VEHICLE MILEAGE GIVEN IS APPROXIMATE. THE PASSENGER ESTIMATES THE SPEED AT ABOUT CITY STREET SPEEDS AT TIME OF ACCIDENT SINCE THE CAR WAS SLOWED TO GET ON THE SHOULDER. THE ACCIDENT IS COMPLICATED BECAUSE THE DRIVER CAN'T REMEMBER MUCH OF WHAT HAPPENED BEYOND SHE WAS PULLING OVER TO THE RIGHT SHOULDER TO CHANGE DRIVERS OR REST, BUT THE FRONT SEAT PASSENGER WAS ABRUPTLY WOKEN UP FROM A SCHEDULED NAP BY WHAT SEEMED TO HIM LIKE A POTHOLE OR PERHAPS AN ABRUPT EDGE TO THE ROAD FOLLOWED QUICKLY BY A ROUGH RIDE. WHEN HE OPENED HIS EYES HE SAW THE CAR ON THE WILD CLUMPS OF GRASS LIKE VEGETATION ON THE OUTSIDE OF THE REFLECTOR STAKE LINE AND AN ODD SHOULDER THAT WAS ONLY PARTIALLY CEMENT OR PAVEMENT WITH A SUBSTANTIAL GAP BETWEEN THE SIDE REFLECTORS AND HARD SURFACE. THIS WAS SEMI-CONFIRMED WHEN REENTERING WYOMING WITH HIS OLDEST SON DRIVING AND SEEING SIMILAR PARTIAL SHOULDERS, BUT THE SON WAS UNWILLING TO DRIVE FARTHER TO THE ACCIDENT SCENE. THE PASSENGER'S BELIEVES THE TRACTION CONTROL ENGAGED AND CAUSED THE CAR TO GO OFF THE SHOULDER, IN PART BECAUSE OF A SIMILAR PROBLEM WITH A GEO PRIUS LSI ABS BRAKE SYSTEM ON ICE THAT CAUSED WHAT WOULD HAVE NOT OTHERWISE HAVE BEEN SIGNIFICANT VEHICLE DAMAGE. THE ALTERNATIVE EXPLANATION IS A DEFECT OR DEBRIS ON THE SHOULDER ITSELF. THE DRIVER TRIED TO GET BACK ON THE HIGHWAY INSTEAD OF FOLLOWING THE SLIGHT CONTOUR DOWN OF THE SHOULDER OUTSIDE RIGHT OF WAY AND THAT OR TRACTION CONTROL MAY HAVE CAUSED THE CAR TO LEAVE THE PARTIAL SHOU