The present wording of implementing the regulation for type-approval of motor vehicles and engines with respect to emissions from heavy-duty vehicles (e.g., Euro VI requirements) describes the procedure to determine gaseous emissions from on-road measurements using Portable Emissions Measurement Systems (PEMS). Emissions to be measured according to the PEMS protocol are carbon monoxide (CO), total hydrocarbons (HC) nitrogen oxides (NOx) and carbon dioxide (CO₂). Measurement methods of particles will be included in the Euro VI requirements.Emission results from on-road testing can be used for In Service Conformity (ISC) pass/fail criteria but also for establishing emission factors for specific routes and verification of the fuel impact on the emissions. During onboard measurement, emission sampling, measurement of the exhaust parameters and recording of the engine parameters as well as ambient data shall continue throughout the normal in-use operation of the vehicle, i.e., driving conditions that are mostly used by the operator or fleet owner of the particular vehicle type.During the past years a PEMS pilot study has been carried out in Sweden, supported by The Swedish Transport Agency, in order to verify the emissions from different types of heavy-duty vehicles and fuels.This paper presents some of these results with focus on evaluating the impact on emissions measured with a PEMS instrument with regard to different alternative fuels such as Fatty-Acid Methyl Ester (FAME), Dimethyl Ether (DME), Ethanol and Compressed Natural Gas (CNG) when the vehicles are driven on the road during a normal working day. The results are compared with emissions from a diesel vehicle.