No more peeking under the restroom doors trying to spot a pair of shoes; Los Angeles International Airport is testing out a green/red light system that indicates whether a toilet cubicle is vacant or occupied.

The “Tooshlights” system installed at 20 restroom stalls in American Airlines’ Terminal 4 displays a red light outside when a door latch is shut, and green when it is unlatched.

The system also provides data about restroom usage to the airport. Barbara Yamamoto, chief experience officer at Los Angeles World Airports (LAWA), said the system should “help improve our guest experience and allow us to better monitor and service our restrooms.”

“The real-time data that we will be receiving through our new smart restroom technology will help us to respond quicker when issues occur, and gain base-line data for daily and weekly restroom usage, so we can better plan and deploy our resources, including custodians, and maintenance workers,” said Michael Christensen, deputy executive director of the facilities and maintenance group at LAWA.

Availability of restrooms is one of the top concerns of LAX customers, research has shown.

“A common problem in facility design is flow of movement, which affects passenger satisfaction,” said Allen Klevens, president and chief executive officer at Modus Systems LLC, the parent company of Tooshlights.

“Tooshlights is disrupting the public restroom industry by fixing the efficiency of restrooms, especially in large commercial spaces like airports, where people are pressed for time.”

Airport officials said Tooshlights could be added at more LAX restrooms if they pilot program proves successful.