The invention relates to a system comprising a plurality of first sensors to measure parameters characterizing a vehicle operating state; a second sensor to measure a parameter characterizing an emission of an fuel processing apparatus; a control device to measure repeatedly over a predefined time period and to determine a vehicle operating state based on a first data set with measured values from the plurality of first sensors and predefined parameter ranges describing a predefined vehicle operating state; an allocation device to allocate a second data set comprising measured values from the second sensor to the predefined vehicle operating state; and an evaluation device to determine a characteristic value for assessing or optimizing the operating behavior of the vehicle based on the vehicle operating state and the second data set, wherein the characteristic value characterizes an energy efficiency of the vehicle or an emission behavior of the fuel processing apparatus.