C182 PLT MAKES FORCED LNDG ON HWY.

Narrative

I WAS FLYING AS ONE OF THE STAFF TOW PLTS. ON JUL/SUN/02; AFTER APPROX 2.3 HRS OF FLYING; I CONTACTED GLIDER OPS TO INFORM THEM THAT I WOULD BE GOING TO THE ZZZ1 TO REFUEL. GLIDER OPS ASKED IF I HAD ENOUGH FUEL TO MAKE 2 MORE TOWS BEFORE REFUELING. I LOOKED AT MY GAUGES AND READ JUST OVER 5 GALLONS IN THE R TANK AND JUST OVER 10 GALLONS IN THE L TANK AND RADIOED THAT I COULD MAKE 1 MORE TOW. AFTER THE TOW; I PASSED OVER THE FIELD TO DROP THE ROPE AND HEADED N FOR THE 15 MIN FLT TO ZZZ1. APPROX 4 MI OUT ON CLBOUT; THE ENG QUIT. I PICKED A SPOT ON THE ZZZ1 HWY FOR LNDG; MADE A RADIO CALL BACK TO GLIDER OPS THAT I WAS GOING TO LAND ON THE HWY; AND SAW THAT THE GAUGES WERE STILL READING APPROX 13 GALLONS WITH ABOUT 9 GALLONS IN THE L TANK. I SWITCHED THE FUEL SELECTOR TO L; BUT THE WIND MILLING PROP DID NOT START UP. I LANDED ON THE HWY WITHOUT INCIDENT; WAITED FOR ASSISTANCE; FUEL; AND CLRNC FROM THE STATE POLICE TO TAKE OFF. THE CAUSE OF THE PROB WAS IMPROPER FUEL MGMNT; UNDERESTIMATING THE FUEL BURN RATE UNDER TOWING CONDITIONS (WHICH CALCULATED OUT AFTER THE FACT AT 14.6 RATHER THAN THE TYPICAL 11 GPH) AND RELIANCE ON FAULTY FUEL GAUGES. PREVENTION WOULD BE ADDRESSED BY MORE CONSERVATIVE FUEL ESTIMATES AND MORE FREQUENT VISUAL CHKS WITH THE STICKS.