Waze sent me an early notice about the Garmin Marathon in Kansas City, but this morning the directions took me to a crossing spot that was going to be jammed for a long time. I know my way around fairly well, so I took a 10min detour and drove in that route without any delays. Is there no way Waze could suggest these open routes as an alternative to the ones that get you stuck and severely delayed? After all, the organizers of the marathon do share estimated clearing times for specific intersections along the run route.
Great suggestion. Without seeing that exact intersection, it may have been left open allowing routing to consider going across at a particular point. Depending on the marathon and organizers they might block all routing across a given route, or they might leave open particular points if law enforcement officers are controlling an intersection and periodically allowing traffic through. So closures might have been present, but if the cross routing wasn’t blocked, you end up with the scenario that you encountered.