NEW YORK — On the London Underground, Piccadilly Circus station is nearly vacant on a weekday morning, while the Delhi Metro is ferrying fewer than half of the riders it used to. In Rio de Janeiro, unpaid bus drivers have gone on strike. New York City subway traffic is just a third of what it was before the pandemic.

A year into the coronavirus pandemic, public transit is hanging by a thread in many cities around the world. Riders remain at home or they remain fearful of boarding buses and trains. And without their fares, public transit revenues have fallen off a cliff.

In some places service has been cut. In others, fares have gone up and transit workers are facing the prospect of layoffs.

That’s a disaster for the world’s ability to address that other global crisis: Climate change. Public transit offers a relatively simple way for cities to lower their greenhouse gas emissions, not to mention a way to improve air quality, noise and congestion.

“We are facing maybe the most important crisis in the public transit sector in different parts of the world,” said Mr Sérgio Avelleda, the director of urban mobility for the World Resources Institute and a former transport secretary for São Paulo, Brazil. “It’s urgent to act.”

But act how? Transit agencies that have been bailed out by the government are wondering how long the generosity will last, and almost everywhere, transportation experts are scrambling to figure out how to better adapt public transit to the needs of riders as cities begin to emerge from the pandemic.

For now, people simply are not moving around much. Even in cities like New Delhi, where most businesses are open, many office workers are working from home and universities have not resumed in-person classes. Paris has a 6pm curfew.

In some places, fear of the virus has driven people into cars. In the United States, used car sales have shot up and so have prices of used cars.

In India, a company that sells secondhand cars online saw sales swell in 2020 and its own value as a company jump to US$1 billion (S$1.35 billion), according to news reports. Elsewhere, bike sales have grown, suggesting that people are pedalling a bit more.

The worry about the future is twofold. If commuters shun public transit for cars as their cities recover from the pandemic, that has huge implications for air pollution and greenhouse gas emissions.

Most importantly, if transit systems continue to lose passenger fare revenues, they will not be able to make the investments necessary to be efficient, safe and attractive to commuters.

There are a few outliers. In Shanghai, for example, public transit numbers took a nosedive in February 2020, but riders have returned as new coronavirus infections remain low and the economy rebounds.

But the picture is grim in many more cities.

On the Paris Métro, ridership was just over half of normal in the first two months of this year. Île-de-France Mobilités, the transport agency for the greater Paris area, said it lost 2.6 billion euros (over S$4 billion) last year. The agency is projecting a shortfall of an additional billion euros this year.

In Amsterdam, ridership numbers on the city’s trams and buses are around a third of normal, and the transit agency’s website counsels people to “only travel when absolutely necessary.” In Rome, Metro ridership remains below half of pre-pandemic levels.

One of the busiest metro systems in the world, the London Underground, which normally clocks around four million journeys every weekday, is currently operating at around 20 per cent of its normal capacity. Buses are a bit more populated, running around 40 per cent of normal.

The city transit agency, which had once projected a budget surplus for 2020, has instead been relying on government bailouts since the pandemic hit. It expects it will take at least two years to see public transit usage return to pre-pandemic levels.

“It’s been pretty devastating, to be perfectly honest,” said Mr Alex Williams, director of city planning for Transport for London. “One of our concerns are substantial declines in public transport and higher levels of car use.”

London is one of a handful of cities around the world with a congestion tax designed to reduce car traffic in the city centre. Both London and Paris sought to use lockdowns to expand bike lanes.

In the Indian capital, New Delhi, the subway reopened in September after a suspension of many months. Ridership in February hovered under 2.6 million, compared with more than 5.7 million for the same month the year before, and bus traffic stood at just over half of pre-pandemic levels.

Lucky are those agencies, as in India and across Europe, that are subsidised by their governments. There is even more distress in cities where people rely in large part on private bus companies.

In Lagos, Nigeria, fares have doubled on private bus lines for rides longer than a kilometre, or a bit more than half a mile.

In Rio de Janeiro, a once-celebrated bus network is in a shambles.

The private company that runs the system has cut over a third of its fleet and laid off 800 employees as the number of passengers has shrunk by half since last March, according to the city transportation department. Strikes by bus drivers have made bus travel even slower and more chaotic.

“I have never seen anything like it,” said Mr José Carlos Sacramento, 68, a leader of a bus workers union in Rio, who has been working in public transportation for five decades. “I think it might never go back to normal.”

City officials said they hope to use the crisis as an opportunity to revamp the system, including by persuading the private bus companies to be more transparent about their operations in exchange for possible financial help from the government.

After all, said Ms Maína Celidonio, the head of the city transportation department, a clean, efficient bus system is critical for Rio to not only reduce its carbon emissions but also to clean its air.

“It’s not just an environmental issue, but a public health issue,” Ms Celidonio said.

The bigger challenge for all cities is to fix their public transit systems now so that passengers will return, said Mr Mohamed Mezghani, head of the International Association of Public Transport.

They could adjust peak hour service as telecommuting from home becomes more commonplace, expand bus only lanes that make commutes more efficient and comfortable or improve ventilation systems to assure citizens that riding public transit is safe.

“Those cities that were investing, they will get out stronger,” Mr Mezghani said. “People will feel more comfortable traveling in a new modern public transit system. It’s about perception in the end.” THE NEW YORK TIMES