Since vehicles are becoming more and more efficient, this lowers the values measured in the test cycle. At the same time, if the higher consumption due to comfort/convenience functions not covered by the NEDC remains constant, the difference increases as a percentage. While other technical factors play only a minor or even no role on the dynamometer, they have a considerable effect under real driving conditions. For example, aerodynamics, a key efficiency factor in long-distance driving, is left out of consideration in the NEDC. The WLTP takes account of all optional extras with an influence on vehicle aerodynamics, rolling resistance, vehicle mass or power consumption. The only exception in the first stage of the WLTP is the air conditioner. This means that, in most cases, WLTP consumption values will be higher, yet more realistic.