The buses of the emerging geographies have an image problem. Imagine lurching, creaking buses, bolted together back in the '70s, lined up bumper-to-bumper on an exhaust-choked thoroughfare and under the hazy sky of a chaotic urban center somewhere outside the Western world.
That's the standard vision of an outdated, ramshackle approach to moving millions of people around a growing city (throw in the bus driver's collection of saints and other idols glued up on the dashboard to complete the picture).
In Bogotá, Colombia, though, the much-maligned city bus has been getting a decade-long makeover. TransMilenio, a Bus Rapid Transit (BRT) network in Bogotá, was among the first to tackle the massive challenge of urban mobility by focusing more, not less, on buses. In fact, TransMilenio was the first new major mass transport system in the world to use only buses.
Bogota's success has resulted in dozens of other cities around the world following its path. Mexico City, Beijing and Bangalore, India, are among the cities seeking relief from traffic congestion through the BRT approach to bus transport.
It helps that each BRT system takes only two to three years to build, compared with the much more complex and expensive process of getting a subway system up and running—35,000 passengers per direction per hour, with a capital cost of $18 million to $20 million a mile, as compared with $1 billion per mile, the price of a typical New York subway line.
Energy-friendly hybrid electric commuter buses—used widely in the United States—are for now prohibitively expensive in developing countries. Nevertheless, the International Energy Agency has concluded that only 10 percent of a bus transit system's climate friendliness has to do with the bus itself.
It's how the bus is used—rather than what makes the bus keeping running—that really counts.
The BRT model is designed around a fleet of buses that travel in dedicated lanes, board at sheltered stations and bypass boarding delays through prepaid fares, provisions that make for a speedier and more hassle-free journey. The BRT model also dramatically changes how the poor—who have been shown to prefer the cheaper buses to the metro—can access goods, services and jobs.
The BRT era began with a pioneer trunk line built in Curitiba, Brazil, but it has found its most famous expression in Colombia, a country known for its 75 percent rate of city dwellers in the world's most urbanized continent—80 percent of South American residents now live in cities and 90 percent will do so by midcentury, according to a U.N. report.
TransMilenio "proved that you can serve passenger levels equal to what metro systems were carrying but using BRT," said Dr. Walter Hook, CEO of the Institute for Transportation and Development Policy (IDTP).
TransMilenio's affordability for Bogotá's residents, half of whom live in poverty, has been one of its guiding principles from the start. Free feeder buses that connect to the BRT's main lines transport passengers to and from far-off regions of the city where its poor reside; this portion of users can account for as much as half of TransMilenio's total users.
Within the BRT the same fare applies to everyone, one of the ways in which the system is subsidized. "Public transportation is a big part of making cities more inclusive because it enables low-income residents to access economic opportunities and social services," stated Dalberg, a global development advisory firm that has studied the affordability of TransMilenio for the poor, in a report.
A large part of TransMilenio's success comes from a structure which combines private and public funding, said Oscar Edmundo Diaz, head of the Bogotá transport and urban planning firm GSDplus. There are several major players involved in TransMilenio's funding: the national government, which pays for 70 percent of its infrastructure, such as corridors, stations, garages and public space (the other 30 percent is paid by the city); public bids for private fare collection and bus operators; and a private trust fund which disburses the system's income weekly.
A percentage of the fares goes back to TransMilenio to help pay for its operations, such as the programming of buses, the system's growing plans and supervision of contracts. Part of TransMilenio's road maintenance comes from a tax on gasoline. TransMilenio buses are made by companies in Peru, Chile, South Africa and France.
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While the the public-private partnership mode should improve TransMilenio's chances of becoming self-sustaining, the system is showing signs of structural stress. "TransMilenio's first corridors [which covered some of the city's most popular routes] were more profitable since they had more passengers and, as the system grows, the new corridors will be making less profit," Diaz said.
The BRT movement has included notable miscalculations and public relations nightmares, too. The failure of TransJakarta BRT to adopt feeder routes which have been successfully used in other rapid bus systems, including Bogota's, has been cited as one of the key reasons for its present struggles.
There have been traffic bottlenecks (Delhi), and even rioting—in 2004, residents of Bogotá protested the overcrowding on TransMilenio buses and, in 2012, the system again ground to a standstill as demonstrations broke out over an increase in fares and deterioration of service quality.
A decade into the Bogota experiment, the marquee Colombian BRT system and its many followers have come to a crossroads. Yet despite the fiasco in Delhi, Indian cities such as Ahmedabad, Pune and Indore now have a few BRT corridors.
Another achievement has been Mexico City's Metrobús, which has run a large network of BRT lines since 2005 while striving to raise awareness of its environmental impact.
China, in addition to having some 20 BRT lines, is planning to go a step beyond. Since 2010, engineers have been trying to develop a so-called straddling bus, otherwise known as the 3D Express Coach, to deal with city traffic—a futuristic-looking double-decker with a hollow first floor that allows faster-moving cars to pass underneath.
Managing the politics of urban transit has arguably proven even more difficult than figuring out the logistics of making the system sustainable. The ongoing protests in Brazil began over an announced increase in bus fares in Sao Paulo, a city equipped with several BRT lines.
With transit systems being the most visible, and easily targeted, aspect of a city, they can quickly become a lightning rod for citizens' discontent. Further out, though, they could become an increasing number of cities' best bet for moving millions of residents through the maze of a 21st century megalopolis.
—By Katherine Foshko Tsan, Special to CNBC.com.