Remote sensing is one technique used to measure real-world NOx emissions in Europe. Remote sensing measurements conducted by the Canton of Zurich are unique in terms of how consistently they have been collected since 2000 and the steep road grade at the main remote sensing monitoring site. This paper compares the remote sensing measurements and emissions in Zurich to a large dataset of other European remote sensing measurements—the so-called CONOX database—focusing on the effect of estimated engine load on NOx emissions.