Along Delhi\'s traffic-snarled streets, three-wheeled motorized rickshaws dodge and dart amid the swarms of diesel-belching cars and trucks. Years ago, India\'s second-largest city hoped that by requiring auto rickshaws to run on clean-burning natural gas, it could solve pollution concerns, while supporting growing transport needs. Delhi now boasts of one of the world\'s largest fleets of vehicles fueled with compressed natural gas (CNG), but the city\'s transport woes continue. Each day, hundreds of thousands of commuters stand on Delhi\'s treacherous roads, scrambling to find an available three-wheeler at a fair price. The headache of urban transportation drives even more Delhi dwellers to buy cars, feeding a vicious cycle that further worsens congestion. Delhi alone has 11 percent of the nation\'s private vehicles but just 1.4 percent of the population. Think tanks, city governments, and entrepreneurs say boosting auto rickshaw use could help reduce dependency on cars and improve air quality. But finding the right mix of policy and incentives has been a struggle, especially when many among the growing middle class in India consider car ownership a status symbol as much as a transport solution. But without major reforms in transportation—including investment in short-haul solutions such as cleaner-burning auto rickshaws-the snarl of cars and lung-burning pollution in Indian cities will quickly get worse, as the nation\'s urban population swells from a total of 340 million people today to a projected 590 million by 2030. Auto rickshaws, also called \"tuk-tuks,\" or just \"autos,\" are motorized versions of the three-wheeled pulled or cycle rickshaws that long have provided essential transportation throughout the developing world. As their numbers grew in India\'s cities, so did concerns about the pollution spewed by their typical diesel-fueled two-stroke engines. Simple and cheap two-stroke engines, common in chainsaws and lawnmowers, cause higher emissions than the four-stroke engines used in cars due to incomplete combustion. The Delhi government sought to deal with this issue by taking steps to convert auto rickshaws within the city to cleaner-burning CNG. But at the same time, a 1997 Supreme Court decision, citing pollution concerns, capped their number at 55,000. But that policy approach has proven problematic in a city that includes the nation\'s capital, New Delhi, and with a skyrocketing population of 11 million that is second in India only to Mumbai\'s. The number of private cars is growing fast and there are fewer rickshaws than needed to meet demand. In November 2011, the Supreme Court lifted its cap, a move that will allow 45,000 more auto rickshaws onto Delhi\'s streets. With nearly all of Delhi\'s motorized three-wheelers running on CNG and most of them using four-stroke engines, the hope is that the small private taxis will truly be a cleaner solution. Advocates point to the success of entrepreneurs like 26-year-old Sulabh Mehra, who started up his pioneering Radio Tuk-Tuk business, just outside Delhi, in the sprawling suburb of Gurgaon, two years ago. His innovation was to offer a dial-up service supplied previously only by full taxis. Instead of flagging rickshaws on the street, commuters could dial direct for a rickshaw ride. \"Commuting is a major issue in Gurgaon,\" says Mehra. \"We service the last mile [of] connectivity from your home to public transportation. For longer distances, prearranged \"autos\" [rickshaws] can cut back on cab use.\" Mehra\'s distinct, bright-red autos stand out from the standard green-and-yellow ones that buzz through Gurgaon. His fleet has doubled to 100 auto rickshaws in two years, transporting about 1,000 people a day in the suburb of more than 1 million people. A virtually untapped market, clearly, there is business potential. Similar models have popped up across India. But getting people to give up their coveted cars in favor of bumpy, open-air tin rickshaws won\'t be easy. About 1,200 new cars hit the streets of Delhi each day. Horn-slamming taxis, luxury sedans, and SUVs take up about 90 percent of the road space, but cater to less than 20 percent of the transportation demand. (Related: \"China\'s Electric Car Drive: Impressive, But Not Enough\") \"Why would I want to take an \"auto\" [rickshaw] when it is a huge hassle?\" asks Preethi Bansal. Her family is part of India\'s booming middle class. They live about a mile from the Delhi metro but have four cars for their family of five. To discourage car use and boost rickshaws, \"tax policies need to change,\" says Akshay Mani, of the sustainable transport nonprofit EMBARQ. \"People who choose to drive a car should pay higher taxes and parking fees,\" he says. Instead, the government heavily subsidizes diesel fuel, leading citizens to opt for cars that run on one of the dirtiest fuels available. In 2000, diesel cars accounted for just 4 percent of India\'s market. They now make up 40 percent of new car sales, and soon are expected to hit 50 percent. \"Commuters need to have viable options of transport other than cars,\" says Mani, who explored the potential of auto rickshaws as a solution in a February report on India\'s urban transport for the World Resources Institute. Mani wrote that by making rickshaws safer and increasing the distance they could travel, the government can make them a sustainable part of the transport system. In an analysis of several Indian cities, Mani\'s report showed that auto rickshaws are playing a significant role as a transportation option, accounting for between 10 and 20 percent of daily trips made on motorized road transport, even though they account for just 2 to 11 percent of the total number of motor vehicles. The Supreme Court\'s decision to lift the cap on the number of auto rickshaws in Delhi is designed \"to cater to the ever-growing demand,\" says the city\'s head transport secretary, R Chandramoihan. Experts have welcomed the shift in policy and intention, saying it can\'t come soon enough. \"Investment in an improved transport sector has been much slower in Delhi [than elsewhere in India],\" says, Anumita Roychowdhury, executive director at the Delhi-based Centre for Science and Environment. \"Delhi has been car-centric with a phenomenal expansion in bridges and highways.\" But not everyone is convinced the needed reforms will take place, or if they do, that they will change much in the end. Corruption is a problem, with drivers often paying thousands of rupees [1,000 rupees equal about $19] for a Delhi rickshaw permit on the black market, and five times the usual cost for the actual rickshaw vehicle. This often translates into higher fares for commuters. \"I don\'t see any change happening,\" says Rakesh Agarwal, head of the Nyaya Boomi nonprofit, which is working to promote rickshaw drivers\' rights. \"There is a mafia that runs the rickshaw business in Delhi and they are not likely to let [a new influx of competitors into the market]\" Mehra of Radio Tuk Tuk agrees. While his Gurgaon business has been a success, he says he is prevented from expanding into Delhi because of mafia control and high rickshaw prices. Meanwhile, the number of cars increase and the pollution problem worsens. Commuters\' lungs burn and their chests tighten as they breathe Delhi\'s noxious air, rife with toxic particulates in concentrations five times higher than those deemed safe by the World Health Organization. India has the world\'s worst air pollution, worse than China\'s, says a January study by researchers from Yale and Columbia universities who track air pollution by satellite. Those who suffer most are the elderly, sick, and young. Acute respiratory infections are contributing to more child deaths each year, says Dr. S.K. Kabra, a respiratory physician at Delhi\'s main hospital, the All India Institute of Medical Sciences. Outside Kabra\'s office, hundreds of parents line up with their children, coughing and struggling to breathe as they wait for appointments. One by one, he listens to their chests. Through frequent checkups, he hopes to keep these kids from becoming another grave statistic. More than 13 percent of children under 5 die in hospital care for respiratory infections in India, according to the World Health Organization, though there are likely many more cases that go unreported. \"Pollution increases the morbidity, increases the frequency, increases the severity,\" Kabra says. \"We need to improve our environment to improve the health of our people in India.\" Delhi is looking at a variety of solutions, including scaling up the public transport system of buses and commuter trains, improving walking and cycling infrastructure, as well as making parking reforms and adding more transit-oriented development. Delhi\'s master plan, in fact, has set a target of 80 percent of trips by public transportation by 2020, compared to about 40 percent today. This would mark a significant change in current trends, with auto rickshaw journeys growing at about 5 percent, while private car and motorbike trips are moving ahead at 12 percent and 15 percent annually. An auto rickshaw strategy will be an essential element of this effort, experts say. But they say Delhi will require aggressive action on many fronts to protect its economy and citizens from being choked by road congestion.