The Port Authority just put out a bid package for the construction and delivery of two carfloats. While I still think my scaled-up version of 'Las Plumas' is a good alternative, it looks like they have made the decision to go with conventional, albeit longer, carfloats. I took a good look at the drawings, which call for a single ended float, four tracks wide, with a capacity of 18 sixty foot cars.
I think they could gain some efficiency if they made these floats double ended. If both ends are identical allowing loading and unloading from either end, more trips could be made in a given time period by eliminating the need to turn the float around when docking. The additional length, which would come from adding a second bow, could hold two more cars. The Staten Island Ferry wastes no time in turning around to dock, right?
As designed, or with my suggested 'tweaks', any harbor tug of appropriate size could handle these carfloats. But going back to my idea of an electric powered 'Las Plumas', an electric powered tug might be a good alternative. Using the Articulated Tug/Barge concept (ATB) as a starting point, why not have a dedicated tug attached to the barge alongside? Attached at the floats midpoint by a large 'hinge', the tug could use it's azimuthing propeller to turn itself around while the float is being loaded and unloaded. Electric cables for charging the tug's batteries can be run through the hinge, barge and then ashore for power; again, the batteries being charged while docked.
I think the Port Authority has the right idea, but perhaps it could be developed a bit more. An electric powered carfloat system should be able to get some development money, tax credits or tax benefits.