You've probably heard that L.A.'s transit system is growing. Young people are embracing urban life, renting lofts in the Arts District and selling their cars so they can take public transportation. And L.A. leaders are adapting to give them what they want, providing WiFi at bus stops and building new rail lines faster than any other city.

There's one problem with this story, and that's that ridership is actually dropping. Yes, at a time when employment is up, and the rail network is growing, fewer people are taking buses and trains.

According to the Metropolitan Transportation Authority, ridership peaked in April 2014 and has since declined by about 5 percent. Some statistics show an even steeper drop. In the third quarter of 2015, bus ridership was off 9.3 percent compared with the same period in 2013.

This is unusual, and the MTA is struggling to explain it.

For now, they don't have one grand theory. They cite a number of factors that may have combined to curtail ridership.

Dan Nguyen, an MTA deputy executive officer, noted that undocumented immigrants now are eligible for driver's licenses. That gives them the option to drive when they might otherwise have been forced to take public transportation. The licenses became available in January, and the state has issued more than 500,000 of them.

“Probably more than half of them come from our buses,” Nguyen said.

However, that doesn't explain why ridership would have dropped after April 2014. Conan Cheung, an executive officer for finance, cited several other potential factors.

On the rail side, the agency has been working to repair the Blue Line, which is 25 years old. That has led to service disruptions. Blue Line ridership is down 9 percent since 2013.

Ridership is also down on the Red Line (6.6 percent), the Green Line (12 percent) and the Orange Line busway (9.9 percent). Cheung noted that service issues also have beset the Green Line. The MTA recently closed turnstiles on the Red Line and did more fare checking on the Orange Line to discourage fare evasion, which may explain the decline on those lines.

The two newest lines, the Gold Line and the Expo Line, have seen overall increases since 2013. However, even the Expo Line is down 6 percent from its peak in 2014.

On the bus side, Cheung noted that several other agencies in Southern California and around the country are seeing reduced ridership on their bus lines. Transit officials note that passengers seem to be migrating to rapid service. Lines with infrequent buses are shedding passengers, while those with faster and more convenient service are seeing increases, Cheung said.

In recent months, transit officials have developed an “action plan” to address the declines. The agency is looking to expand some of its rapid bus service, and to make existing bus lines more efficient by reducing bottlenecks. They're also trying to improve communication with the general public about service delays.

The numbers, Cheung said, “are telling us we have to do something different with the system. We need to put the focus on speed, frequency and reliability.”

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