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The present wording on implementing regulation on type-approval of motor vehicles and engines with respect to emissions from heavy-duty vehicles in Europe (e.g., Euro VI requirements) describes the procedure to determine gaseous emissions from on-road measurements using Portable Emissions Measurement Systems (PEMS). The gaseous emissions to be measured according to the PEMS protocol includes carbon monoxide (CO), total hydrocarbons (THC) and nitrogen oxides (NOx) for diesel engines and with the addition of methane (CH₄) for gas engines. Measurement methods of particles are at this stage under development. Emission data from on-road testing can be used for calculation of In-service Conformity (IsC) pass/fail criteria but also for establishing local emission factors for specific routes. The procedure for the measurement is described in detail in the regulation.

Motor vehicles are seldom used in ambient conditions like those defined in current emission regulations. For example, most of the year average temperatures across Europe fall much below the range of legislative testing. Furthermore, it has been widely demonstrated that cold-starts at low ambient temperature increase the emissions. Therefore, there is a growing need to broaden the range of legislative emissions tests and set a separate low-ambient test with respective emission standards. This paper gives emissions test results form a joint research programme between Sweden and Finland. Altogether 11 late model gasoline-fueled TWC vehicles were tested at ambient temperatures of +22 and -7 °C using a variety of different driving cycles. Apart from the driving schedule, other test parameters like vehicle preconditioning, manual vs. automatic transmission and the effect of external cooling were studied and discussed.