The sun rarely shines in Linfen. It rises in the morning, of course, but its rays barely make it past the thick cloud of smog that hangs over this northern Chinese city.
At street level, residents regularly wear masks to avoid inhaling too much of the putrid air.
Linfen has the dubious distinction of being one of the most polluted cities in the world, a place where taking a simple breath can make you ill. While nearby coal mines are a major culprit, the city is also overrun with automobiles. Cars and motorcycles are the main mode of transport there, as public transit is almost nonexistent. The city averages roughly one bus for every 2000 people -- one of the lowest rates in China.
Linfen's transit woes are typical of the developing world. Urban areas from Argentina to Angola struggle with extremely poor transit service, perpetuating critical issues like poverty and pollution. Without sufficient bus or train routes, some cities barely even manage to sustain themselves.
"There's no way to overestimate the value of a public transit system," says Nancy Kete, director of the World Resources Institute Centre for Sustainable Transport. "Without it, people are so disconnected that the city doesn't function as a single unit."
Many of these cities in Africa, Asia and South America had public transit systems in the 1950s and 1960s, but simply couldn't afford to keep them. Buses fell into disrepair, services suffered and eventually collapsed. By the 1990s, poor funding spelled an end to government-run transit in urban areas of Peru, Venezuela, Chile, and a number of other countries.
Private operators filled the void, mostly in the form of shared taxis and minibuses, but they're often unreliable and expensive. In Nairobi, for example, shared buses only leave when full, resulting in long delays. They are also heavy polluters and a hub for petty crimes such as pickpocketing.
But impoverished residents have no other choice, meaning that access to education, employment, local businesses and government services are a constant struggle. Basic mobility becomes a luxury and entire cities suffer.
"If a city doesn't have a transit system, people can't get to work or school," Kete explains. "That doesn't support the economic base."
In countries like China and India, where a new middle class is emerging, poor public transit means cars have quickly become the preferred mode of transportation. This doesn't bode well for air quality though, especially since these countries already have lax environmental laws.
In China alone, the number of vehicles on the road has skyrocketed in the past decade -- from one million to 20 million -- contributing to the country's terrible air pollution. According to the World Bank, 16 of the world's 20 most polluted cities are now in China.
Kete says that, in addition to the fundamental role public transit plays in a city's sustainability, well-funded bus and train services are also one of the best ways to combat global warming.
In 2002, her organization partnered with Mexico City to build a 20km rapid bus line. Since completion in 2005, it has reduced carbon dioxide emissions from city traffic by an impressive 47,000 tons a year, and has drastically reduced commute times.
So there is a huge opportunity for the international community -- both aid organizations and governments - to improve lives in the developing world by investing in its public transit systems, something which Kete calls the "backbone" of any well functioning city.
This sort of ongoing commitment of time and money has nearly limitless benefits for developing cities and their residents. And with more than half the world's population now living in urban areas, when they benefit, we all do.