The changes will see the first of hundreds of new carriages being introduced by ScotRail, Virgin Trains East Coast and Caledonian Sleeper on routes within the country and linking London.
A further set of vintage trains are being refurbished by ScotRail after operating between London and the west of England.
Experts said the network had not seen anything like it since the rapid expansion of the railways more than 150 years ago.
Rail consultant Allan McLean said: “I don’t recall a year benefiting Scotland so much with new trains since Queen Victoria was just a young lass. The coming months look promising.”
McLean, an industry veteran who worked for Virgin Trains West Coast and British Rail, said: “Some of what is planned would have been great years ago. It augurs well for the future of rail travel in Scotland, particularly if the opportunity is taken to maximise the number of seats with the greatest possible comfort.”
First up are due to be new Japanese-designed Hitachi electric trains for the main Edinburgh-Glasgow line, which will then be spread to a number of other routes across the Central Belt. They were scheduled to have started carrying passengers in September, but manufacturing delays and problems with the £795 million electrification of the line are expected to put this back to late March, as The Scotsman has revealed.
The trains will have more carriages and be able to accelerate faster than the existing diesel trains, providing more seats and cutting journey times between Scotland’s two largest cities by ten minutes to 42 minutes by the end of 2018.
They will be followed by new Caledonian Sleeper trains, which are due to start operating between Scotland and London in April.
The Spanish-built carriages will include the first double beds in a British train, and ensuite cabins with showers.
Then in May, ScotRail is planning to introduce refurbished but roomier 40-year-old InterCity 125 High Speed Trains between Edinburgh/Glasgow and Aberdeen and Inverness.
By the end of the year, they will be joined by the first of Virgin Trains East Coast’s new Azuma fleet, on the east coast main line between London, Edinburgh, Aberdeen and Inverness. These will cut most Edinburgh-London journeys to four hours by 2020.
Passenger watchdog Transport Focus said travellers eagerly awaited the improvements. Passenger director David Sidebottom said: “Passengers will be pleased to hear new trains are on their way.”