Agreement on plans to look at three-hour Scotland to London rail link
The Scottish and UK governments have reached an agreement with the long-term aim of three-hour train journeys from London to Scottish cities.
The move came alongside the publication of the HS2 Ltd report on extending a faster rail service to the north of England and Scotland.
The two governments announced that work on evaluating options for the project would begin next year.
They said "implementation" of the plans could begin in 2019.
It currently takes at least four hours to travel from Edinburgh or Glasgow to London - and frequently much longer.
Scottish transport secretary Keith Brown said: "Doing nothing is not an option."
The cost of the suggestions range from £17bn to £43bn, although some improvements could be introduced in stages.
'Build on improvements'
New track could be built either side of the Pennines, or bypasses introduced on sections of the existing East and West Coast Main Lines where speed is constrained.
Robert Goodwill, the UK minister responsible for the second high-speed line (HS2), said: "Scotland will benefit from HS2 from the day it opens, with shorter journey times to London from the start.
"Once the full Y-Network opens, it will only take about three hours 38 minutes to reach London from Glasgow and Edinburgh. This report looks at ways we can build on these improvements and I thank HS2 Ltd for this work.
"Together with the Scottish government, we will be asking Network Rail to identify any options with a strong business case, for consideration for inclusion in future plans."
The first phase of the high-speed line to the English midlands is due to open in 2026.
The "Y" network, extending the service to northern English cities, is scheduled for completion in 2033.
What is HS2?
The initial plan is for a new railway line between London and the West Midlands carrying 400m-long (1,300ft) trains with up to 1,100 seats per train.
They would operate at speeds of up to 250mph - faster than any current operating speed in Europe and would travel up to 14 times per hour in each direction.
This would be followed by a V-shaped second phase taking services from Birmingham to Manchester and Leeds. Intermediate stations in the East Midlands and South Yorkshire are also planned.
Backers of the project have claimed it could bring £3bn of benefits to Scotland.
The options included in the new publication include upgrading the existing cross-border lines and building new routes.
Mr Brown said: "This report is a major milestone in the campaign to deliver high-speed rail to Scotland and marks the beginning of the next chapter in the tale.
"I now have a firm commitment that development work will begin during the current control period towards getting journey times between Scotland and London down to three hours or less.
"High speed rail will bring billions of pounds worth of benefit to Scotland's economy and an infrastructure project of this magnitude - possibly the biggest Scotland's ever seen - means jobs, investment, benefits for the economy and benefits for the environment."
The HS2 Ltd report Broad Options for upgraded and high speed railways to the North of England and Scotland was welcomed by the two ministers at a reception in Edinburgh's Waverley station.
Last week, train operator Virgin unveiled its new Azuma trains, which will be launched in 2018. It said it hoped most journeys between Edinburgh and London would be reduced to about four hours.