This can't be answered without argument as :-
Do we take into account the manufacture of each vehicle ?
as the making of the steel and forging plus making of the bits must have been very 'dirty' with the eight wheeler.
The car won't be mutch better as the battery ,motor components ,and tyres are a bit naughty to make
The train :- runs on steam which has to be generated some way by burning coal/oil.
How effecient is the train? how many 'stationary boilers' need to be kept burning to make use of it.
The Life time of each vehicle needs to be known. (and you know what us brits think of american cars

).
How much coffee or tea is drunk while opperating.
Is the car charged from coal/wind/nuke/tidal/water wheel ?
The IC engine in the car "what fuel will it run on"
I could go on all night But i realy like the eight wheeler

Steve