I just went through a little exercise I've been meaning to do for some time, and check how much wider the OSCARS actually are.

The formula for the offset from the track centre of a train car going around a curve is:

O = Wb x Wb / ( 8 x r ) + Wd/2

(Actually a first order approximation accurate to at least 0.1% for this calc - it basically assumes the curve is a big parabola rather than a circle). WB = Wheel base, Wd = Width.

From Wikipedia & the (now defunction) CityRail Website drawings of V Sets and OSCARS:

OSCAR Width: 3034mm

V Set Width: 2930mm

OSCAR Wheel Base: 12700mm

V Set Wheel Base: 15700mm

As the OSCAR's have a shorter wheel base their additional offset going around a curve is less than the longer V car.

Plugging numbers into my formula:

On no curve the OSCAR offset is 1.517 vs 1.465 for a V, a 52mm difference being the extra width of the train.

For a typical mountain 300m corner:

OSCAR Offset = 1584

V Curve = 1568

The difference is now 18mm

But on a tight 200m curve,

OSCAR Offset = 1618mm

V Set = 1619mm

I haven't found a published precise definition of "Extended Medium Gauge" that includes maximum allowable wheel base, but according to ARTC's

http://www.artc.com.au/library/GI_05_loading_restrictions.pdf , the unrestricted loading gauge for NSW is:

width: 2970 mm (2890 below platform height it must be said)

with 16155 mm.

On those numbers, vehicles meeting the unrestricted standard for NSW need *more* lateral space than an OSCAR on curves sharper than 500m (at least above platform height).

Does anyone know what the 10 tunnel's track centre spacing is? Because based on this little analysis, even those should be fine for the OSCARs so long as they can fir through in a straight line, not just the curves (300m if I read the Track & Curve diags correctly).

As I see it, the only possible issue could be platforms, and that is a relatively simple thing to sort out - if it needs to be done at all. More likely an appropriately qualified engineer needs to supervise checking/measuring the actual loading gauge and sign off on allowing OSCARs on it.