The northern bank of the River Main in downtown Frankfurt between Alte Brücke and Untermainbrücke was closed to motor vehicles for a year. The objective behind the temporary closure was to examine the subsequent impact this had on traffic. The “before/during” study was destined to provide evidence-based insights for a political decision on the definitive closure and conversion of the section of the riverbank. This was only possible to a limited extent for the “during” study owing to the COVID19-related changes to traffic flow. AS+P planned the traffic-side measures necessary for the closure, such as adapting road markings, signage and traffic-light programs at the surrounding nodal points. Within the city limits, the relevant signage was changed and over a large area dynamic and static signs deployed to highlight the closure. For the residents and other users in the immediate area, AS+P together with the City of Frankfurt Dept. of Transportation developed individualized solutions in consultation with the persons and organizations affected. During the closure AS+P studied the changed traffic volume at 10 relevant nodal points as well as the changes in travel time in the surrounding network, which provided insights into how traffic flows shifted. The increase in pedestrian and cycle traffic on the riverbank section in question and on both sides was likewise monitored. The most important piece of evidence for the politicians was provided by the representative poll of Frankfurt citizens that AS+P prepared: The majority of the Frankfurt citizens (57%) wanted a permanently redesigned riverbank section closed to motor vehicles; only 21% were against this option.