ON 12/14/2015, I WAS DRIVING ABOUT 60-65 MPH ON A MARYLAND HIGHWAY AT AROUND 10AM. I WAS IN THE NEXT LANE BESIDE THE FAST LANE. THE 2011 MAZDA CX7 STARTED TO DECELERATE. I LOOKED DOWN AT THE GAGES TO MAKE SURE I DIDN'T INADVERTENTLY GO INTO NEUTRAL. I WAS STILL IN DRIVE. I HIT THE BRAKE, NOT COMING TO A COMPLETE STOP, AND THEN STEPPED BACK ON THE GAS, PUSHING THE GAS PEDAL TO THE FLOOR AND THE CAR WOULD NOT ACCELERATE. IT WENT DOWN TO ABOUT 20 MPH. IN MY REARVIEW MIRROR I SAW A TRACTOR TRAILER COMING TOWARD ME AND THERE WAS NO WHERE I COULD MOVE, AND I COULD NOT SEE ON THE OTHER SIDE OF THE TRAILER TO GO INTO THE NEXT LANE WITHOUT HITTING ANOTHER VEHICLE. I WAS HIT IN THE REAR BY THE TRAILER. I HAD ON MY SEATBELT AND THE AIRBAG DID NOT DEPLOY. I CHECKED FOR CARS IN THE FAST LANE AND SLOWLY MOVED ONTO THE SHOULDER. THE DRIVER OF THE TRUCK FOLLOWED ME. I PURCHASED THE CAR USED LAST YEAR FROM MILE ONE IN BALTIMORE, MD. THE CAR FAX FOR THE VEHICLE WAS GREAT, WITH NO ISSUES. I GOT OIL CHANGES EVERY 6K MILES, MY LAST ONE BEING IN SEPTEMBER 2015, AT JIFFY LUBE. THIS WAS MY FIRST INSTANCE WITH ANY ACCELERATION AND DECELERATION ISSUES. IF THERE WAS AN ISSUE, I DID NOT GET ANY INDICATION LIGHT ON MY DASH BOARD THAT THERE WAS AN ISSUE.