Interstate Tunnel Fire Alarm Systems

Recently while traveling through Phoenix along the I-10, I noticed in some of the larger tunnels have Fire Alarm Pull Stations. These tunnels also have hydrants, fire exits, and suppression systems. The only reason I could see these Pull Stations is to contact Phoenix Fire Department since cell service may be disrupted in there.

What may be some other reasons?

Maybe the tunnel has a suppression system

That is exactly correct - tunnels tend to be protected by water spray/deluge systems. They tend to be far more common in Europe than they are in the United States, but they do exist and Tyco makes some interesting literature about it: The Total Fire Protection Solution for Tunnels | Tyco Fire Protection Products

The aforementioned pull stations are probably marked “ AGENT RELEASE “

I assume so, they also have 911 call boxes since it is a pretty big tunnel.

Yeah because suppression panels don’t have dialers

Possibly, you also have to note that ADOT (Arizona Department of Transportation) has a traffic monitoring station in the Deck Park Tunnel. The Pull stations and call boxes probably connect to that station.

2nd note, The Deck Park Tunnel that @WheelockNS is mentioning is actually 19 Bridges cemented together. So it’s not actually a tunnel. It may or may not have an agent release system because of this, but it’s hard to tell if there is when you’re going 65 on a large freeway.