Communter Rail between NOLA and Baton Rouge

Not to mention the cost of buying up enough land for a right-of-way for a six-lane and all of its cloverleaf exits, as opposed to two rail lines and some station parcels.

More people would live upriver from N.O. and downriver from BR. More commuter trains to and from those neighborhoods than all the way between cities, until demand indicated otherwise.

Rail systems like this are always going to lose money intially, but so do toll roads. Rail systems with buy-in can give your city a real downtown, as opposed to the plasma-like state of such megacities (by footprint) such as Atlanta and L.A.