The other day, I was sitting in the back of a new Audi A8, lounging in my heated, reclined seat and playing with the silly tablet controls as me and my friends swept through the Holland Tunnel from Manhattan to New Jersey enjoying some bops on the radio. Then I realized how weird it was to have the radio still playing in the tunnel.
Having passed through plenty of tunnels in the past with the radio notably cutting out until reaching the grace of the warm sunlight on the other end again, I made a note to myself to look it up later. And here we are.
As it turns out, it’s not that hard to get radio signal in a tunnel, though you, the commuter, can’t really do much to improve your chances. Instead, the tunnel has to have its own radio transmitters installed for it to work, and some of them do.
A tunnel radio transmitter works the same way a big FM radio station transmitter works, by amplifying a signal through an antenna to produce the FM radio waves that are picked up by your car, just on a smaller scale and underground.
The Holland tunnel got AM radio back in 1985 and FM radio transmitters in February 2001, according to the Port Authority. Radio equipment in the tunnel’s ventilation buildings pick up the outside FM signal, and then broadcasts the signal into the tunnel through wall-mounted antennas.
The tunnel radio systems aren’t just to prevent drivers from losing their favorite Oldies classics in rush hour gridlock returning to their idyllic New Jersey suburbs, though. The system can be overridden by the Port Authority to transmit traffic, safety and security information directly to each car’s radio in the event of an emergency.
Shorter tunnels don’t always need tunnel transmitters, though. If it’s short enough, the short FM wavelength makes it more likely to bounce off surfaces like the road or tunnel walls for some distance, unlike the long wavelength AM signals that are much more likely to be blocked before they can bounce.
More importantly these days, tunnel transmitters could also be used to transmit cell phone signal inside the tunnel, to keep your Waze navigation accurate and the Spotify chugging along, though you lose the excuse of dropping the call you don’t want to be on in the tunnel.
Everything has a trade-off.