She received a prepaid Oyster travel card at the event at Paddington Station, in west London on Tuesday, but did not use the train herself.
The Queen attended with her son, Prince Edward, and was welcomed by British Prime Minister Boris Johnson and London Mayor Sadiq Khan.
The Elizabeth line is named after the British monarch.
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The 96-year-old monarch has struggled with mobility issues and has canceled several performances in recent months, including the opening of parliament last week.
Opening parliament is an important constitutional responsibility and cannot take place without the monarch. The Queen had to delegate that responsibility to Charles, Prince of Wales and William, Duke of Cambridge, who are state advisers.
Known as Crossrail under construction, the Elizabeth Line was built on a much larger scale than the city’s existing “Tube” lines. The first phase will open to the public on May 24.
The Queen depicted with an Oyster ticket machine.
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The 62-mile network is built around a core consisting of 42 miles of brand new tunnels through central London, dug with incredible precision beneath one of the most developed cities in the world.
At the height of construction, Crossrail was Europe’s largest engineering project.
The twin tunnels, 20 feet in diameter and up to 40 meters (130 feet) deep, weave around building foundations, London underground tunnels and countless other structures and facilities.
Between 2012 and 2015, it took them three years to dig with eight 1,000-ton tunnel boring machines.
Pre-pandemic projections predict that about 200 million passengers per year are expected to use the Elizabeth line when fully open, but that number has been questioned by rapidly changing work patterns.
Ben Jones of DailyExpertNews contributed to this report.