After years of delays, London’s over-budget Elizabeth line rail link finally opened to passengers on Tuesday, with hopes it will speed up journeys across the British capital and provide an economic boost.

The railway, which was initially called Crossrail before it was renamed in honor of Queen Elizabeth, offers faster journeys from Heathrow Airport and Berkshire in the west to Essex in the east through a series of new, long tunnels under Britain's capital.

It is expected to carry 200 million people a year and will increase London's rail capacity by 10%, according to Transport for London (TfL).

London Mayor Sadiq Khan and Transport for London Commissioner Andy Byford traveled on the first westbound service that departed Paddington at 6:33 a.m. (5:33 a.m. GMT), accompanied by hundreds of rail enthusiasts and a few commuters.

Khan called the opening "historic" and "the most significant addition to our transport network in decades."

"The Elizabeth line is much more than just a new railway – it will provide a crucial economic boost to the whole country and help to turbo-charge our recovery from the pandemic," Khan told reporters.

"We should be incredibly proud of this fantastic new line, it is 22nd century fit," he said. "It’s spacious, silent, comfortable; this is the game changer we need."

Construction started more than 12 years ago on Europe’s biggest infrastructure project at the time. In 2010, the project was budgeted at 14.8 billion pounds and was set to open in December 2018.

Delayed by issues with safety testing and signaling systems, even before the onset of the pandemic, Crossrail has opened three and a half years late and more than 4 billion pounds over budget for a total cost of 18.8 billion pounds ($23.6 billion).

Khan's predecessor as mayor, Prime Minister Boris Johnson, said the project is forecast to boost the U.K. economy by 42 billion pounds.

"Absolutely delighted that the Elizabeth Line has opened to the public today," Johnson said on Twitter.

"Long-term investment in U.K. infrastructure pays off – with this project alone supporting 55,000 new jobs, 1,000 apprenticeships, and forecast to boost the U.K. economy by £42 billion," Johnson wrote.

Passengers will be able to interchange with London’s Tube – the world’s oldest underground passenger railway – and the line is on the famous London Underground map.

But its scale dwarfs the Underground, with Class 345 trains that are more and than one and a half times longer than a Tube train and able to carry 1,500 passengers.

Colin Kelso, an 18-year-old rail fan, traveled down from Glasgow to travel on the debut service.

"I’ve never been able to explain why I’m in love with trains, but I guess it’s just this new multimillion-pound investment has been created, and to say I was the first person on it," he said. "It’s such an achievement."

Only one of the line's three branches has opened.

Initially, 12 trains per hour will run in each direction through the middle section of the line, which includes 21 kilometers (13 miles) of tunnel, linking Paddington in the west to Canary Wharf and Abbey Wood in the east.

Sections from Shenfield, east of London to Liverpool Street and Heathrow Airport and Reading, west of the capital, to Paddington will open by May next year, allowing services to nearly double.

Trains are currently scheduled to run from 6:30 a.m. to 11 p.m. Monday to Saturday, with a Sunday service expected to start later this year.