Environmental damage and climate change, air pollution, energy efficiency, fuel consumption and emissions are subjects for studies and legislations worldwide. Brazil must therefore be prepared to follow global trends in energy optimization tests and developments, including Euro 6 equivalent emission legislation. Considering the worldwide tendency for Real Driving Condition Test for heavy vehicles, the authors, using the developed Towing Trailer Prototype provided with an electromagnetic brake, performed fuel consumption on-road tests. For measuring fuel consumption on-road or on testing tracks, the developed system allows initially measurements with an independent auxiliary tank for short distances and measurement with an auxiliary tank connected with the truck tank for long distances. The tests were performed on road in real conditions initially by maximum speeds of 75 km/h. In a first and second LAP, tests were performed without electromagnetic braking, having checked the effectiveness of the methodology as well as the resultant dispersion of consumption measurement. In the third and fourth LAP, tests were repeated in the same section of the road with two different levels of electromagnetic braking, simulating different uphill. In a fifth LAP, measurements were repeated with Trailer tires with lower pressure. The influences of those parameters were evaluated, showing double the fuel consumption with the maximum tested electromagnetic current and 50% higher by using lower tire pressures. Other 3 LAPS ware performed by maximum speeds of 90 km/h and indicate a possibility to run at these speeds. The tests indicated a very interesting possibility to perform on-road fuel consumption tests until 90 km/h with Towing Trailer provided with electromagnetic brake. Measurement devices and methodologies should be optimized in future tests.