This briefing paper summarizes the relevant provisions of current EU and U.S. regulations, reviews what is publicly known about automakers' positions with respect to those provisions, and contributes an independent engineering perspective where relevant. The intent is to provide context for evaluating proposals to reform the regulations governing passenger vehicle type approval and real-world testing in Europe. The paper highlights ambiguities in EU regulation as it presently stands—and potentially in any regulation patterned on it, as many national vehicle emissions regulations are.