Real-time arrival information for the L train is now available on smartphone apps, the MTA said yesterday.

The L train is the first of the lettered lines to have its arrival information available for third-party app developers. The information can also be found on the MTA's Subway Time app for the iPhone and on the web. Subway Time launched December 2012 with arrival times for the Nos. 1, 2, 3, 4, 5 and 6 trains, and the 42nd Street shuttle.

The addition to the MTA's Subway Time was made possible by the L train's modern Communications-Based Train Control signal system. Real-time information for the No. 7 train could be added to Subway Time next after the line gets a signal upgrade that's expected to be completed in 2016.

The MTA said the rest of the letter lines will be added to Subway Time and get station countdown clocks within five years. But that will not require a similar upgrade to the new signal system, according to MTA spokesman Aaron Donovan. Digital equipment can be added on top of the existing decades-old system.

"This would be a workaround that lets us add real-time info even though the subways will not be getting a modernized signal system during that time frame," Donovan said.