The Caledonian Sleeper is one of my favourite ways to get to London. You can sleep while you travel overnight, so you don't waste time during the day. There are, in fact, two Caledonian Sleeper trains, each with multiple portions. The Lowland Sleeper serves Glasgow and Edinburgh, splitting and joining at Carstairs. Sensible enough. But then there's the Highland Sleeper, which serves Fort William, Inverness and Aberdeen, but it splits and joins at Edinburgh. Why Edinburgh and not Carstairs? OK, for the Aberdeen portion, Edinburgh isn't much of a diversion, but for the Fort William portion, it seems rather inefficient to drag the portion to Edinburgh, to have to take it all the way back to Glasgow to get to the West Highland Line. Plus it runs for a fair old distance on diesel power under the wires.
Which brings me to the other issue: traction choice. Back when DB Schenker were providing the traction, the sleeper was hauled by Class 90s for the electric part of the journey down the West Coast Main Line, and by Class 67s (which replaced Class 37s) north of the central belt. Sensible enough. However, when GBRF took over the contract, they switched to Class 92s for the electric-hauled part of the journey (still sensible enough), but for the diesel-powered part of the trip, they chose... Class 73s. What? These were electro-diesels built for the Southern Region of British Railways, primarily for routes that were electrified by DC 3rd rail in the south-East of England, with a diesel engine for bits of track where 3rd rail power was unavailable. They were certainly not built for dragging sleeper trains over the mountainous West Highland Line. Anyway, GBRF overhauled them, installed new engines, and had them double-head with Class 66s when more power was required.
Now let's be honest, the Sleeper doesn't need to be fast. It's a sleeper train; people expect it to take 8 hours or more so they can get a good night's sleep. However, routing the Fort William and Inverness portions via Edinburgh does seem highly inefficient from a fuel use standpoint if nothing else. So, how would I improve its efficiency? First of all, forget Edinburgh. Route the Highland Sleeper through Motherwell instead. Take off the Fort William portion there and send it via Whifflet and Gartcosh to join its current route via Queen Street low level. The Aberdeen portion can take the Falkirk Grahamston route to the Forth Bridge and Fife to join its present route, and the Inverness portion can carry on to Stirling, Perth and Inverness. Alternatively, if we take Fife off the Highland Sleeper's itinerary, the two portions could split at Perth, however this would still require changing to diesel traction at Stirling. As an alternative, Fife could be served by extending the Edinburgh portion of the lowland sleeper to Dundee via the Forth and Tay bridges.
As for traction, GBRF is planning to replace its current locomotives with bi-mode Class 99s, so that problem is likely to solve itself fairly soon.
