Measurement methods and weighting factors used to calculate typical emissions values for agricultural tractors are primarily developed for other types of vehicles and the results cannot be assumed to be representative of agricultural driving conditions. The purpose of this work was to calculate speci"c emission test weighting factors for a range of typical agricultural tractor work operations. The aim was also to compare emission values calculated using the general standardized weighting factors with values obtained using weighting factors typical for speci"c operations.
In order to calculate new weighting factors, time series from sensors mounted on a standard medium-size tractor were recorded during typical agricultural operations. The data recorded were then used to calculate engine speed and loading torque. The recorded points were divided into groups, one for each of the test modes in the standard, and the weighting factors calculated from the relative amount of recorded points in each group.
One major conclusion is that the amount of emissions from the tractor engine, measured relative to the output power from the engine, show very large variations depending on the characteristics of the work operation. The use of one single set of weighting factors not adapted to the speci"c operation may therefore give very incorrect results.