California's new 220-mph bullet train won't begin accepting passengers until at least 2025, three years later than the initial schedule, according to a new business plan released by the agency overseeing the long-gestating project. But there's a silver lining: the high-speed rail line between San Francisco and Los Angeles will only cost $64.2 billion, or almost $4 billion less than originally estimated.

San Francisco to LA at 220 mph

The main obstacle is figuring out how to cross the mountains of Southern California. The high-speed rail authority thought it could do it by 2022, but now they admit it will likely take three years longer. The 2016 business plan, which was released last month, says that the plan became more complex since Californians approved it in 2008. How complex? The LA Times analyzed the project last year and concluded it would require drilling 36 miles of tunnels through the earthquake-prone mountains north of LA, some of which are still unmapped.

As such, the mountainous passage outside LA won't be built until the end of the schedule, while the San Francisco leg of the project will be built first. And while the high-speed rail authority was able to trim some costs, finding enough money, especially private investment, remains a huge challenge, the agency's chairman Dan Richards told the Times. "If we had started with all the money in the world, this program would have probably proceeded differently," he said. "If we did not have some of the requirements of the bond act, this program would definitely have proceeded different."

The dream of high-speed rail in the US, especially high-trafficked corridors like SF-to-LA or New York City to Washington, DC, has long been the dream of transportation advocates, especially as major cities in Europe and Asia build and perfect their own bullet trains. The lack of high-speed rail, and the resulting traffic jams, is what inspired billionaire inventor Elon Musk to design the hyperloop, which he argues could travel at twice the speeds of high-speed rail at a fraction of the cost. But while his system has its supporters, it is still a long ways off from being a viable mode of travel. Until then, the high-speed rail, and all its complexities, will have to suffice.