The government is launching a review of the high-speed rail network, from London to Birmingham and to Manchester and Leeds, known as HS2.
There has been concern about cost, the exact route of the line and its effect on those living near it.
What is the HS2 route?
The initial plan is for a new railway line between London and the West Midlands carrying 400m-long (1,300ft) trains with as many as 1,100 seats per train.
The line would carry trains capable of reaching speeds of up to 250mph and would run as often as 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.
The Department for Transport has said that the project would triple the capacity of trains across the entire route.
If the project goes ahead, a new HS2 station would be built next to Manchester Piccadilly as part of the second phase – from Crewe to Manchester and the West Midlands to Leeds.
The programme originally began under the Labour government in 2009. It is the second High Speed rail project after High Speed 1, which links St Pancras International and the Channel Tunnel, and opened in 2003.
When will it open and how much will it cost?
The government’s review of HS2 will consider whether and how the project should proceed. Government officials have refused to rule out scrapping the project entirely, despite delays and billions having been spent already.
The first phase of the railway – between London and Birmingham – is due to open at the end of 2026.
The Public Accounts Committee has cast doubts on this deadline. A letter from its chairwoman Meg Hillier in July expressed concern, calling it “unrealistic”.
The onward legs to Manchester and Leeds could start being built in the middle of the next decade, with the line fully open in 2032-33.
In July, the current chairman of the project, Allan Cook, reportedly warned that the total cost could exceed the current budget of £56bn by £30bn.
Mr Cook was appointed to head HS2 in December 2018 after his predecessor resigned because of delays at the Crossrail project in London, which he was also leading.
In a Westminster Hall debate, former Commons leader Andrea Leadsom recently claimed the bill for the high-speed rail line could top £100bn.
What about journey times?
The Department for Transport says the project will cut Birmingham to London journey times from one hour 21 minutes to 52 minutes.
Once the second phase is complete, Manchester to London journeys would take one hour seven minutes (down from two hours seven minutes), and Birmingham to Leeds 49 minutes (down from two hours). This would effectively reduce journey times between London and Edinburgh and Glasgow by an hour to three-and-a-half hours.
The government hopes its creation will free up capacity on overcrowded commuter routes.
What about fares?
There has been no announcement on ticket prices.
The government previously said its proposals “assume a fares structure in line with that of the existing railway” and that HS2 could generate sufficient demand and revenue without needing to charge premium fares. It originally estimated total fare revenues of up to £34bn over a 60-year period.
What about opposition to HS2?
Some MPs argued that the construction of HS2 would create thousands of jobs.
Others believe that it could be a catalyst for economic growth and could help rebalance the economy between the North and South.
However, HS2 will pass through about 70 parliamentary constituencies, and local groups opposed to the scheme are lobbying their MPs to vote against the plans.
There is political pressure on some Conservative MPs in particular, some of whom oppose the project as the route will pass through their constituencies,
Pressure group Stop HS2 believes that the operation of the line will cause increasing carbon emissions, as well as damage to areas of natural beauty and the ecosystems they support.
It has also accused HS2 of “sending out possession orders like there is no tomorrow”, referring to the compulsory purchase of properties in the path of the line.
HS2 Action Alliance has previously argued that it believes a disproportionate number of the 30,000 jobs created around HS2 stations in phase one will be in London.