supply question

[Volcano Man]

Looks like the bridge and road is across a stream, not a river (although it is hard to tell). Bridges at streams have no effect on reduction of VST supply level, but bridges across rivers prevent it.

But, more importantly, AFAICR only roads affect VST supply level because it is supposed to represent supply trucks, not trains (VST = Virtual Supply Trucks). Unless I am mistaken, rails are not factored into the equation.