I’ve always that the concept of a funeral procession to the cemetery was sort of grotesque. After all, everyone just mourned for the poor schmuck at the church/synagogue. What’s the point of the journey to the cemetery just to see the guy planted in the ground?
Perhaps for the family, that act provides some closure, but for everyone else, the cemetery thing seems rather tribal and antiquated.
But to address the question: where I live (Georgia) there are rent-a-cops that will stop traffic for the entire length of the funeral procession, even if it blocks major arterial and collector roads. Stopping traffic for 5 minutes of a procession can muck up an intersection for 40 minutes in recovery.
Suppose an ambulance/fire truck needs to get through? Does the emergency vehicle have precedence over the dead guy?