The Utah Transit Authority, along with various other agencies, will test emergency response protocols during a live-action drill scheduled Wednesday.

But don't worry, it's only a test.

UTA, in conjunction with the Utah National Guard 85th Civil Support Team, the FBI Joint Terrorism Task Force, Salt Lake City International Airport, Salt Lake City Fire Department and the Salt Lake City Police Department will conduct the exercise called “Operation Green Cloud.”

The exercise will be a six-hour, full-scale emergency response drill simulating an attack on a Green Line TRAX train.

The exercise will take place on the TRAX platform at Salt Lake City International Airport and will simulate a terrorist device detonating aboard a light-rail train ...

The drill will evaluate responses to an attack, specifically allowing emergency responders to test its procedures for recovering and decontaminating passengers in addition to examining protocols for executing tactical chemical, radiological and explosives response measures...

“We’ve got signage all over the platform and the operators will make announcements that an exercise is in progress,” Cornell-Titcomb said. The event will run from 4 p.m. through 10 p.m.

The exercise area will be marked off and closed to the public to avoid interference with normal train service, interruption of the exercise and to provide for the safety of the public. Access to the immediate area of the drill will be limited to exercise players, evaluators, controllers and safety personnel....