Protection of the civilian population is the responsibility of the armed forces controlling them. Comingling civilian evacuees with military traffic is a war crime because the military traffic is fair game. Using a ferry/bridge for civilian evacuations that are also used for military traffic is irresponsible and could rise to the level of a war crime. There are accepted protocols for civilian evacuation, like a negotiated evacuation corridor monitored by neutral observers. Russia has not attempted to arrange such a corridor, and it is Russia’s responsibility to initiate the action; see my first point. In short, Russia can’t send civilians across the same river crossings used for military operations without negotiating a temporary, supervised cease-fire. Of course, the optics of this would be horrible, and so Russia will continue to risk civilians if not outright use them as human shields.