A man rides a new Line 4 subway train linking the Ipanema and Barra da Tijuca neighborhoods of Rio de Janeiro during a media tour on Saturday. (Mario Tama/Getty Images)

RIO DE JANEIRO — To the relief of organizers, the government and the tens of thousands either working on the Games or planning to watch them, Rio finally began operating its new Olympic metro line at 6:07 a.m. on Monday.

It came in the nick of time, just days before the Olympics opening ceremony on Friday. After security worries, plumbing and electricity complaints at the Athletes' Village, and the destruction of a ramp at the sailing marina by waves last weekend, something finally went right. The Olympic waters may still be dirty, but the metro link is shiny and new.

The new line’s first passengers, a dozen or so Rio 2016 volunteers and staffers, were happy to see their commuting time slashed.

“It is a legacy for the population,” said Elizabeth Murta, 60, a former gymnast from the city of Belo Horizonte and one of the many pensioners volunteering at the Games. She said the line will help a dream come true — working at the gymnasts' training area. “There are many positive things that people don’t see,” Murta said of the Games.

The new line, originally promised for 2014, had caused increasing nervousness as its opening was repeatedly postponed. Further frazzling nerves, the Rio state government, responsible for its construction, declared a state of “public calamity” over its finances in June, forcing an $870 million bailout from the federal government. The state is running a $6 billion annual deficit.

Adriano Melo, 37, a food and drink manager at the Olympic Park, said the new line’s 17-minute journey to the Jardim Oceanico bus terminal in Barra da Tijuca had slashed his daily commuting time.

“It’s very quick,” he said. “I liked it very much.”

Even so, Melo had a 15-minute wait before he could embark on the 20-minute, eight-mile trip on a new bus rapid line that took him on to the Olympic Park.

And the first metro station he tried, called Nossa Senhora da Paz and one of five on the new line, was closed when he got there at 6 a.m. A security guard told him that it hadn’t been inaugurated — even though interim president Michel Temer officially opened the new line on Saturday.

During the Games, only those with tickets and credentials can use the new line’s limited service, which has manually operated trains running every eight minutes. The line will close Aug. 21 and open again during the Sept. 7-18 Paralympics Games. From Sept. 19, it will operate just four hours a day. Regular passengers won’t get full service before the end of the year.

Some transportation experts have criticized authorities for not rigorously testing the new line using passengers. Thiago Magno, a spokesman for Metro Rio, who rode the first train, said tests had been done with bags of sand instead.

Critics said the new metro benefits the upmarket neighborhood of Barra, with just 300,000 inhabitants, instead of other, more densely populated and less affluent areas. But many in Rio will see it as an important transportation legacy. When the line is finally fully operational, it will make popular Barra centers, such as the cavernous Riocentro conference center and the park where the biannual Rock in Rio concerts take place, much more accessible to all.

“It’s very important for the city,” said Leonardo Farrah, 27, who on Monday took the first train to his job on a telecom service desk in the Olympic Park. “Rio invested in buses and transport above ground, which was not very intelligent because they carry less people.”

Rio is the fourth-most-congested city in the world and has a limited, two-line metro network. Line 1 connects Ipanema in its south zone to the center and edges into North Rio. Line 2 splits off to more distant, North Rio neighborhoods.

The new line is called Line 4. Magno said that this is because there is a Line 3, designed to serve areas on the other side of Guanabara Bay, that is still just on paper. The rest of this metropolis of more than 6 million people is served by overcrowded buses or the three bus rapid transit lanes built for the Games, linking Barra to outlying parts of the city such as the international airport and the Deodoro Olympic Park.

On Monday, exclusive lanes for “Olympic Family” vehicles started operating on other major Rio arteries, causing traffic to grind to a halt and some motorists to complain that a 30-minute journey had taken three hours, the G1 news site reported. Rio city hall wanted to charge motorists trying to sneak into the restricted lanes $460 fines, but a judge suspended that move. The fine is $39.