The Highway 99 Tunnel may not be easing Seattle’s gridlock, but at least tunnel travelers will get cell service while they are stuck in traffic 200 feet underground. Thanks to a network of technology systems, there is strong cell service the entire length of the tunnel as well as plenty of safety features. The technology includes 13 miles of fiber optic cables, 95 miles of electrical wiring and 15 miles of lights.

For safety, the $1.4B tunnel is equipped with 300 incident and security cameras, automated ventilation and sprinkler systems and Advanced RF Technologies’ connectivity system that provides a sophisticated antenna system that is spread between five electrical rooms embedded in the tunnel.

The equivalent of cellphone repeaters are installed throughout the tunnel, KOMO News reports. In the case of an emergency, engineers will interrupt the radio to give drivers safety instructions. 

Here are more details on how the system works.