Oh yes RLP'D Opinions foolishness.
Would the final state of a locomotive be spending the energy to keep natural gas at -160c or more compressed natural cars? Of course as a test bed it would be more logical to build a special lng tanker car rather than build six cng cars.
The most logical final state will be a hybrid diesel/natural gas locomotives. When additional power is required for pulling up grade the energy density of the fuel would be increased. Fuel consumption for a train is not so much the weight but getting the weight from inertia to cruising speed.
The six to one density of lng to cng is storage density and not usable energy density. It has the advantage of putting more fuel on board which would be beneficial and flexible until the full infrastructure is in place. Not to mention lng is a far greater investment than simple cng.
Put a simpler way you might be able to understand. You can move a barrel of ethanol around for about $10 in the special tank cars. Real waste on top of everything else for corn ethanol which has not one redeeming benefit.
Now natural gas has 0.036 methanol ml/j of 15.6. Methanol is converted in dimethyl ether (DME) to be used as a diesel replacement
But a large part of the reason rails are going straight natural gas is not free market rational economics or the existing technology tree. If progressives has concern for rationality and pragmatic co2 reduction corn ethanol would no longer exist in America.
So take you bow for the wing monkey dance of the night. LNG for most applications over cng is political not rational. Well know Buffett Progressive rail.