On a quiet Saturday morning at the Hunt Valley light rail station, a train operator called 911 in a panicked voice. “I have just had a rider tell me that someone is coughing and smells something funny in one of the cars,” she said, adding “this is a drill.” With those words uttered shortly after 8 a.m., a full-scale emergency preparedness exercise was launched Aug. 14. Designed by the County’s Office of Emergency Management to gauge the county’s readiness for a mass-causality disaster, the drill depicted a mock explosion and chemical leak in a Maryland Transit Authority light rail car.