DENVER — When you're going down, down, down Interstate 70 through Denver, singing along to Johnny Cash's "Ring of Fire," your radio signal could be overtaken to warn you about a tunnel fire.
"The antenna signals in the tunnel are strong enough to override your radios as you're coming closer," Stacia Sellers, Colorado Department of Transportation's communications manager, said.
CDOT can take over car radio signals to warn of emergencies in the new lowered portion of I-70 near the Purina Plant.
"We have antennas that are, actually, built underground I-70, next to the tunnel that you're driving through. We also have antennas or cables, essentially, that are going over on the ceiling that have strong enough waves that are able to override your radio system to give you important alerts," Sellers said.
The emergency alert can interrupt AM/FM radio signals.
"If there's a car fire, it will tell you that there is a fire and to evacuate the tunnel. These alerts will also go off if there's a tornado in the area, and will tell you what to do and what your next steps are. They can also go off if there's a bomb threat in the tunnel or if there's a hazmat spill as well," she said.
The radio signal takeover is supposed to impact only cars closest to the tunnel.
"If you're over on Quebec Street and I-70, your radio won't be overridden if you are that far away from the tunnel," Sellers said. "Let's say you're 10 cars behind and there's a car fire or you're approaching a fire, your radio will be overridden with the important messaging to let you know how to evacuate."
Evacuating the tunnel would require drivers to leave their vehicles, which is what the emergency message would explain.
"We do have doors in the tunnel, so if there were to be a fire on westbound I-70 underneath the tunnel, you're going to get important safety messaging on how to evacuate to get over onto eastbound I-70. Of course, traffic will be closed off, so you won't be opening the door onto live traffic," Sellers said.
The message is prerecorded and would sound similar to an emergency weather alert that sometimes take over radio stations.
Drivers will hear it if they listen to the radio.
"Any model car. Doesn’t matter how old it is," Sellers said. "The system will not work if you're listening to Bluetooth, if your radio just doesn't work in general, or if your radio is turned off or if you're on a phone call using Bluetooth."
The tunnels also have a series of speakers attached to the roof of the capped portion.
CDOT said those speakers have been used weekly by a traffic operator monitoring the tunnel because of people walking in the tunnel alongside traffic.