Dozens of police and fire units took part in a disaster drill in Seattle's Sodo neighborhood on Sunday.
The exercise simulated a terrorist chemical attack on a passenger train.
Authorities say the drill gives regional agencies the chance to work together and identify potential problems.
"If you don't drill together you get stove piped and you'll only be looking at what you do and not what other agencies are doing. We need a seamless response, not only at the command level but at the tactical level,” said Asst. Chief A.D. Vickery, Seattle Fire Dept.
The drill was funded by a federal grant from the Homeland Security Department.