PORT-AU-PRINCE— Joseph-Marc Carel knows the danger of ferrying passengers on his small motorbike, sometimes two at a time, as tides of the buzzing vehicles cut through the chaotic Haitian capital. He has a prosthetic leg to prove it. Carel would like to find a job that's safer than driving a two-wheeled taxi in Port-au-Prince, but he knows he's unlikely to find one that pays anything close to the $50 a week he can earn with his battered motorbike. "It doesn't look good,'' he said, gesturing at the shattered reflectors and dented red gas tank as he revved the sputtering engine, "but it's mine.'' Cheap motorbikes such as the one that transformed this 24-year-old into an entrepreneur, and cost him his right leg in a 2011 accident, are seen by some as an economic lifeline and by others as a scourge of the streets. The Chinese-made vehicles began to flourish after Haiti's devastating earthquake of 2010, when foreign aid workers brought them in as part of their disaster-relief efforts. Port-au-Prince now is flooded with the small-engine Jialing, Lifan or Jeely models, which can be bought new for about $800 or leased from middlemen. Motorbikes provide one of the most efficient ways to navigate the unpredictable and rutted streets of the teeming capital. But with regulation largely nonexistent, the combination of inexperienced drivers, general lawlessness and packed roadways has resulted in a big jump in accidents. Dr. Bermann Augustin, an orthopedic surgery resident at the Hospital of the State University of Haiti, found in a recent study that motorbikes were involved in nearly 80 percent of all road accidents that sent patients to Port-au-Prince's main general hospital between April 2014 and February 2015. Emergency room administrators say they rarely saw victims of such accidents before the quake. "This has become a big public health problem in Haiti and it's getting worse,'' Augustin said. From her hospital bed in Port-au-Prince, food vendor St. Helene Morissette bitterly describes the accident that fractured her ankle. She was attempting to scurry across a road when a speeding motorbike taxi slammed into her. While she screamed in agony, the driver zipped away without a word. "A lot of these moto drivers are crazy,'' Morissette said while her young son rested his head on her shoulder and a daughter counted cash needed to buy medicine. The Haitian National Police says its officers are trying to crack down on unregistered motorbike operators. But with as many as 500,000 motorbikes on the streets in the greater Port-au-Prince area, traffic division Inspector Jean Yves Pierre acknowledged that authorities are struggling to keep up. The appeal of a motorbike is easy to understand in Haiti. Cars and SUVs often cost twice the price of a new vehicle in the United States and, in any case, are out of reach for most people. According to the World Bank, 59 percent of Haitians live on less than $2.44 a day and 24 percent make do with less than half of that. Even so, the Port-au-Prince area is a traffic nightmare, with SUVs, rumbling trucks and colorfully painted bus-pickups known as "tap taps" competing for space. A trip from the airport to the hillside community of Petionville just a few miles (kilometers) away can take two hours by car. On a motorcycle, the fearless can dart through long lines of vehicles and make it in a fraction of the time. Motorbikes were available in Haiti before the earthquake but they mostly were seen in rural towns, commonly used to carry all types of cargo, including live chickens and pigs, or towing items like rebar, bamboo poles and even wooden coffins from the back. The motorcycles have been critical during Haiti's ongoing cholera outbreak, often serving as the only way to get aid to people in remote corners. And they now make up nearly 45 percent of Haiti's underdeveloped public transportation system, according to official estimates. The influx has been a boon for Haitian repairmen. Luckson Jean, a mechanic who works at a motorbike shop on the outskirts of Port-au-Prince, said the quality of the Chinese machines is inferior to coveted Japanese brands like Honda and Suzuki. They require a lot of maintenance, he said, and even then, generally only last a couple of years. In the hillside shantytown where he lives alone in a one-room concrete shack, Carel is on his fourth motorcycle since his accident. He says he has nightmares that his job may cost him another limb. "But there's no other way for me to survive so I keep going as a moto taxi driver even with one leg,'' Carel says as he straddles his battered motorbike amid the sounds of sputtering engines on a busy street below.