WASHINGTON – If you’ve been on a big city transit system recently, chances are you’ve smelled that distinctive smell: the smell of urine.

One big city has a plan for not only eliminating the smell, but preventing the use of its elevators as portable bathrooms, reports WSBTV.com

The Metropolitan Atlanta Rapid Transit Authority is launching a pilot program in one of it’s elevators.

Officials wouldn’t tell WSBTV which one of its 11 elevators is the focus of the testing, but did explain how it works.

A urine detection device, or UDD, sounds an alarm when someone decides to relieve himself in the elevator. Transit police are also notified immediately.

The pilot program has been in place for a month resulting in a drop in the daily incidents and one arrest.

The UDD’s cost MARTA $10,000 each, WSBTV reports.

WTOP’s David Burd contributed to this report. Follow @WTOP on Twitter.