First responders drilled Thursday for a real emergency inside the new State Route 99 tunnel that runs for two miles under Seattle.

The drill involved eight wrecked cars retrieved from junk yards, and some were posed on their sides. The cars were mixed up with three buses in the simulated accident along with dozens of people simulating various levels of injury to try to give the feel of a real emergency inside the tunnel.

The drill involved the release of artificial “smoke” which was quickly drawn out of the tunnel’s side vents, which are known as louvers, and sucked up and out through yellow stacks you see when driving past the tunnel entrances.

It also involved the setting off of the “deluge” sprinkler system designed to automatically drown a fire or hold a major fire in check until the fire department can arrive.

Also see | 3-week Viaduct closure coming ahead of Seattle tunnel opening

Called one of the most sophisticated tunnels in the world by the agency that had it built, the Washington Department of Transportation, the tunnel is watched 24/7 by operators at the Traffic Management Center (TMC) in Shoreline. Cameras inside the tunnel would automatically turn toward an emergency giving operators a clear picture of what’s going on. Systems like the sprinklers and fans would go on automatically as TMC operators call police and fire.

The detailed drill was aided by the Transportation Security Administration (TSA). Experts from the TSA worked with Seattle police, fire crews, and WSDOT under their Intermodal Security Training and Exercise program (I-STEP).

The TSA is expected to deliver a detailed report around mid-November. Agencies involved may issue their own reports sooner.

Planning for the drill has been in the works for well over a year to try and cover every contingency from the simplest fender bender to a major hazmat incident to terrorism.

Also see | Seattle tunnel delays: Why the project is 3 years late

The tunnel is scheduled to open in early February 2019 after a three-week closure of the Alaskan Way Viaduct.

Traffic in and around the city is expected to see major disruptions during the closure as roads now leading to the Viaduct are redirected into the tunnel.