The electrification of two railway lines is to be restarted after the projects were halted so a review could be carried out, the government says.
Work on the TransPennine Express Railway - between Manchester and York - and Midland Mainline - from London to Sheffield - was paused in June.
Sir Peter Hendy, Network Rail chairman, said the "temporary pause" had "given us the space to develop a better plan".
Transport minister Patrick McLoughlin said work could now resume immediately.
The TransPennine upgrade is expected to provide capacity for six "fast or semi-fast trains" per hour between Manchester, Leeds and York , reducing journey times by up to 15 minutes.
The Manchester to York section of the work is now planned to be completed by 2022.
Once completed, the whole line from Liverpool to Newcastle will be fully electrified, the Department for Transport added.
The electrification of Midland Mainline north of Bedford to Kettering and Corby will now be completed by 2019, and the line north of Kettering to Leicester, Derby, Nottingham and to Sheffield will finish by 2023.
"We face some difficult challenges, and there is more work still to do, but the secretary of state's decision means we can now move forward with our plans to electrify TransPennine and Midland Mainline," Sir Peter added.
By BBC North of England correspondent Danny Savage
There was uproar in June when it was announced that the electrification of the TransPennine route and the Midland Mainline between London and Sheffield was being delayed indefinitely.
Upgrading the TransPennine line between Manchester and York was part of a wider package of measures to improve the rail network in the North, as part of Chancellor George Osborne's ambition to create a northern economic "powerhouse".
When the delay was announced some people commented it was a "northern powercut".
Now the work is to resume.
In June, Mr McLoughlin told Parliament he was pausing both electrification projects - resulting in criticisms from rail users and MPs in the affected areas.
He told MPs he was delaying or cutting back parts of a five-year £38bn plan to modernise the UK's rail network, blaming Network Rail for rising costs and missed targets.
At the time, he said "better services" could be delivered on Midland Mainline before electrification was completed.
Addressing the TransPennine route, he told Parliament in June: "We need to be much more ambitious for that route."
Network Rail then carried out a review of the projects and an update on the projects was delivered to Mr McLoughlin on Monday.
In a letter to Network Rail, the transport minister said work on the two lines could be "unpaused with immediate effect and progressed with some urgency".
He said "connecting up" cities in northern England was "at the heart of our plan to build a Northern Powerhouse".
"This government will see the job through and build a better, faster and more reliable railway for passengers in the North and Midlands," he said.
In June, Labour accused the government of deceiving the public over its decision to pause the two projects, saying it was clear the plans were in "serious difficulty" before May's general election.
Shadow transport secretary, Lilian Greenwood, said: "We warned ministers for months that these projects were at risk, but they cynically waited until after the election to withdraw support."
Ministers had been forced to change course after an "outcry" from passengers after the projects were stopped, she added.
Ms Greenwood accused the government of "incompetence", saying the delays had led to a "damaging hiatus, which had seen construction job losses and resources shifted to other projects".