Interesting proposal. It must be said the idea of closing the line and building a motorway over it was monumental stupidity. I understand it wasnt even a Beeching cut, it was done late 60s. I read somewhere the original idea was to divert all perth services via stirling and the ladybank line was a freight only line. Along with closing the perth-montrose line as well and it adds up to uncompetitive journey times compared to car! I disagree with Jeemac, reopening would greatly aid journey times north to inverness and Aberdeen, however the engineering required to open it will kill it ever happening. It just wont get the capital funding.
There is no way you can thread a new line next to the m90 through glenfarg without demolishing most of the village or cutting into the bank next to the motorway which would require a 30m deep rock cutting. Then as you drop down to the river earn you need a complete new alignment and bridges over the motorway. The only alternative would be to tunnel it, but as the land around glenfarg is so rolling you would need to tunnel from Burnside down to Aberargie, thats 7400m. So I dont ever see it happening unfortunately and now we are left with a short
Somewhere buried deep in transport scotlands 25 year transport plan was the proposal to open a new line between inverkeithing and Hallbeith as others have mentioned. I read the document, it didnt have any design other than a statement of intent. I understand the rationale behind it. It would certainly aid journey times if long distance trains are routed through glenrothes and the cowdenbeath cut off was reinstated. Hallbeith junction is a major interchange and a park and ride would certainly pick up a lot of fife commuting trade. The construction would be expensive though as hallbeith is much higher than inverkeithing.
Inverkeithing S junction is 10m AOD, Hallbeith is 115m AOD and 5400m apart. In addition you have the steep bank that the m90 climbs up directly north of the inverkeithing junction. The line would have an average gradient of 1:55 between these two points so it would need to be in tunnel from the start of the bank to around the junction. Thats a distance of 4500m.
The alternative would be to branch off at north end of Jamestown viaduct and parallel the M90 with a 900m tunnel the west side of inverkeithing through muckle hill with a rising gradient. Cross inverkiething north junction on 1300m long viaduct on a rising gradient, enter a shorter 1000m tunnel of under the bank and come up at dulloch. Average gradient for this would be 1:81 and there would be less tunnelling, but it would miss out inverkeithing station and would involve heavy engineering the entire alignment.
Either way it is expensive, so I am a little cynical it will ever get done.
