On the London Underground, Piccadilly Circus station is almost empty on a weekday morning, while the Delhi Metro carries less than half the drivers it used to have. Unpaid bus drivers have gone on strike in Rio. New York City subway traffic is only a third of what it was before the pandemic.

A year after the coronavirus pandemic began, public transport in many cities around the world is hanging by a thread. The drivers stay at home or are afraid to get on buses and trains. And without their tariffs, public transport revenues have fallen off a cliff. The service has been discontinued in some places. Elsewhere, tariffs have risen and transit workers are facing layoffs.

This is a disaster for the world’s ability to deal with this other global crisis: climate change. Public transportation offers cities a relatively easy way to reduce their greenhouse gas emissions, not to mention a way to improve air quality, noise and congestion.

“We are facing perhaps the most important public transport crisis in different parts of the world,” said Sérgio Avelleda, director of urban mobility at the World Resources Institute and former minister of transport in São Paulo, Brazil. “It is urgent to act.”

But how do you act? Transit agencies rescued by the government are wondering how long the generosity will last, and transportation experts almost everywhere are scrambling to figure out how to better adapt public transportation to driver needs as cities emerge from the pandemic.

At the moment people just don’t move a lot. Even in cities like Delhi, where most of the shops are open, many office workers are working from home and universities have not resumed face-to-face tuition. Paris has a 6 p.m. curfew.

In some places, fear of the virus has driven people into cars. In the US, used car sales have increased, as have used car prices. In India, a company that sells used cars online saw sales soar in 2020 and its own value as a company rose to $ 1 billion, according to news reports. In other countries, bike sales have increased, suggesting that people are pedaling a little more.

The concern for the future is twofold. When commuters avoid public transport for cars while their cities recover from the pandemic, it has a huge impact on air pollution and greenhouse gas emissions. Especially if transit systems continue to lose revenue from passenger fares, they will not be able to make the investments necessary to be efficient, safe and attractive to commuters.

There are some outliers. In Shanghai, for example, public transportation took a nosedive in February 2020, but drivers have returned as new coronavirus infections remain low and the economy recovers.

But in many other cities the picture is bleak.

In the Paris Metro, the number of drivers in the first two months of this year was a little more than half as high as normal. Île-de-France Mobilités, the transport agency for the greater Paris area, said it lost 2.6 billion euros, or more than 3 billion US dollars, last year. The agency is forecasting a deficit of another billion euros for this year.

In Amsterdam, trams and buses in the city are around a third of normal and the transit agency’s website recommends “only travel when absolutely necessary”. In Rome, the number of metro riders remains below half of the preandemic level.

One of the busiest underground systems in the world, the London Underground, which normally makes around four million journeys every weekday, is currently in operation at around 20 percent of its normal capacity. Buses are slightly more populous and drive around 40 percent of normal traffic. The city’s transport authority, which once forecast a budget surplus for 2020, has been relying on state rescue operations since the pandemic. It is expected that it will take at least two years for public transport use to return to prandemic levels.

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March 26, 2021 at 12:43 am ET

“It was pretty devastating, to be completely honest,” said Alex Williams, director of urban planning for Transport for London. “One of our concerns is significant reductions in public transport and increased car use.”

London is one of the few cities around the world with a congestion tax designed to reduce car traffic in the city center. Both London and Paris tried to use locks to widen the bike lanes.

In the Indian capital New Delhi, the subway reopened last September after a break of several months. The number of drivers in February 2021 was less than 2.6 million, compared to more than 5.7 million in the same month last year, and bus traffic was just over half the prandemic level.

Happy are those agencies like in India and all over Europe that are subsidized by their governments. In cities where people are largely dependent on private bus companies, there is even more need.

In Lagos, Nigeria, tariffs on private bus routes have doubled for trips longer than a kilometer or just over half a mile.

In Rio de Janeiro, a once celebrated bus network is jumbled. The private company that operates the system has cut more than a third of its fleet and laid off 800 employees as the number of passengers has fallen by half since March last year, according to the city’s transportation department. Bus driver strikes have made bus travel even slower and more chaotic.

“I’ve never seen anything like it,” said José Carlos Sacramento, 68, chairman of a bus workers’ union in Rio who has worked in public transport for five decades. “I think it could never get back to normal.”

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

According to Maína Celidonio, head of the city’s transportation department, a clean, efficient bus system is vital for Rio to not only reduce CO2 emissions, but also to purify the air. “It’s not just an environmental problem, it’s a public health problem,” said Ms. Celidonio.

The bigger challenge for all cities is now to fix their public transportation systems so that passengers can return, said Mohamed Mezghani, director of the International Association of Public Transport. You could adjust the service at peak times when teleworking from home is the order of the day, widening lanes only for buses to make commuting more efficient and comfortable, or improving ventilation systems to keep citizens safe on public journeys.

“The cities that have invested will come out stronger,” said Mezghani. “People will feel more comfortable in a new modern public transport system. In the end, it’s about perception. “

Shola Lawal and Hari Kumar contributed to the coverage.