Leave it to a high-tech city above ground to build a high-tech roadway underground.

Seattle’s SR 99 tunnel project has a number of noteworthy engineering and construction milestones in the rear view, but as crews work to wrap everything up, the Washington State Department of Transportation revealed Tuesday how much work remains on smart systems — and the operational and safety role all of that tech will play.

Earlier this month, Seattle Tunnel Partners completed work on the double-deck highway. Workers installed the last of the 1,152 road panels that locked together to form the lower/northbound roadway (video below).

But there is still much work to be done to install and test equipment that will ensure the safety of drivers who use the 2-mile route. WSDOT shared some of the details in a new blog post and video (above) which explains how ventilation and fire suppression systems will work.

More than 300 cameras will monitor traffic and security at all times as part of an incident-detection system.

Automatic ventilation systems are designed to keep air quality and visibility high.

Automated sprinkler systems are designed to put out a fire quickly at its source.

After years of watching Bertha, the giant tunnel boring machine, churn beneath the city and the decaying Alaskan Way Viaduct, more numbers attached to the project show just how far we’ve come:

95 miles of electrical wiring.

21 miles of sprinkler pipes.

15 miles of lights.

13 miles of fiber optic cables.

8 miles of linear heat detectors.

WSDOT says thousands of components will need to be tested at least three times — “once to make sure they work, then to make sure they work as a system, then together with other systems to make sure all systems are integrated and functional.”

Once they’re given the go-ahead, WSDOT will hand the project over to a different contractor to align the existing SR 99 and build final ramp connections to the tunnel.

The agency estimates that traffic could be flowing in the tunnel as early as this fall.

Here’s the video of the last roadway panel being installed: