Not sure if posters on this thread are aware that the Quaraiding Grain Bin is well and truly in the top 5 largest receival sites for CBH. Beccause of a couple of key factors related to this line including condition of and cost to rebuild or replace the bridge of the Avon River, lower track standard (gravel ballast) with poor performance in wet months, fairly twisty alignment and the adjoining high standard/high capacity main east-west standard gauge line, there has always been an ongoing debate to close this line and heavily upgrade the road link to Kellerberrin.
I'm aware of a least three studies from around 1980 on this and on each and every occassion the numbers always rated retaining rail as the best option. Its also unfortunate as well that at the time Westrail was heavily rehabilitating much lower standard lines like Newdegate, Hyden, Kalannie etc using recycled 47kg/m rail off the main standard gauge line, that that source of rail was exhausted because had it have been available the Quaraiding Line was the next slated that for rehabilitation that would have included rerailing, insertion of steel sleepers and reballasting with crushed metal ballast in low lying sections. That would have lifted the axleload to 19 tonnes and improved the overall track speed and cycle times as well.
Since that time under the CBH model there is no doubt productivity would have further improved with newer light weight high capacity wagons etc.
I'm still sure that after having previously been exhaustively studied y that the same conclusion that rail on a much upgraded track with the lower cost CBH model
still wins out.