a = index of the rail (running line = 0; ALL distances are referenced to this line). BVE used to be restricted to 15 other running lines (think this has increased now but it is unlikely you will need more than this)
b = offset (metres) in the x direction from the running rail
(-ve numbers = left, +ve number = right)
c = offset (metres) in y direction from the running rail
(-ve numbers = down, +ve number = up)
d = railtype (as defined in the 'with structure' section)
Normally, changes in railtype will be needed when the appearance (curves, ballast colour etc) or sound of a track is to be changed. To change the sounds (eg under bridges), use the train.run command in the with train section to assign a 'sound' to each railtype. A list of the sounds is available on TrainSimCentral.
Rail types can also be changed using the railtype m;n command where m = the index of the rail and n = the railtype.
.Rail x1 = Rail number (anything above rail 0)
x2 = Distance from rail 0 (- for left, normal (+) for right)
x3 = Height from rail zero (- for below, normal (+) for above)
x4 = Rail type (indexed in the .Rail(x) Example/rail.csv area at the top)