DAB+ in tunnels: why underground radio can save lives.

Drive into a tunnel and your radio drops out. Everyone knows it: the music hisses into silence, the voice stutters, and on the other side the signal picks up again. Annoying, but harmless — you think.

Until the moment that radio is the only thing still connecting you to the outside world. Because in a tunnel, your car radio isn't entertainment. It's an emergency channel. And DAB+ makes that channel more powerful than ever — provided the signal is actually there.

The function most drivers don't know about

DAB+ (digital radio) has a property that classic FM never managed as well: the interruption function. A tunnel operator or emergency service can broadcast an emergency message that automatically interrupts the audio playing — even if you're listening to music, a podcast or another station.

Concretely: an incident occurs in the tunnel. At that moment, a spoken instruction can sound through your speakers — "Leave your vehicle, follow the green lighting to the emergency exit" — whether your radio was tuned to that station or not. In an environment where panic and smoke slow everything down, that's the difference between people who know what to do and people who get stuck.

In a tunnel, the radio isn't the soundtrack to your drive. At the wrong moment, it's the voice telling you how to get out.

The problem: DAB doesn't fade weakly — it drops out completely

Here's a technical detail that's crucial for tunnels. Analogue FM dies slowly: as the signal weakens you hear more noise, but you still hear something. Digital DAB+ works differently. It delivers perfect quality up to a certain threshold — and below that it abruptly falls completely silent. No noise, no half-message. Silence.

In the open air that's rarely a problem. In a tunnel — a long concrete and steel tube that completely blocks radio waves — it means that without a special provision, simply nothing gets in. No weak signal to work with. Zero.

That's why in a tunnel the signal has to be actively introduced and amplified, via an installation that guarantees coverage along the full length of the tube. Without that installation, DAB+'s most powerful emergency function is worthless: you can't interrupt a message that never arrives.

Why this is becoming more urgent now

A shift is under way that tunnel and infrastructure managers can't afford to miss. Since 2021, a DAB receiver has been mandatory in every new car sold in the EU. That means the share of drivers listening digitally rises year after year — and that DAB+ is increasingly becoming the standard channel through which traffic and emergency information reaches the vehicle.

Several countries are also gradually phasing out classic FM broadcasts in favour of DAB+. The direction is clear: digital radio is becoming the norm, including for road safety communication. A tunnel equipped today with FM only will soon cover a shrinking share of the vehicle fleet.

The question is no longer whether tunnels need DAB+. The question is whether existing installations are keeping pace with the cars driving through them every day.

More than just emergency messages

Good DAB+ coverage in a tunnel does more than make emergency instructions possible:

• Traffic information keeps flowing, even underground, so drivers stay informed about jams or accidents ahead.
• Seamless transition — the radio doesn't drop out on entry and doesn't have to re-search on exit, reducing distraction.
• Multiple stations at once — DAB+ carries numerous stations on a single frequency block, so every driver keeps their own station until the interruption message comes.
• Integration with tunnel management — the system couples to the existing safety infrastructure, letting the operator intervene in a targeted way.

In short

• In a tunnel, the car radio is an emergency channel, not entertainment.
• DAB+ can automatically interrupt the audio playing with an evacuation or emergency message.
• But DAB+ drops out completely below a threshold — in a tunnel, without an active installation, nothing gets in.
• With the EU requirement for DAB in new cars and the phase-out of FM, digital coverage in tunnels is becoming ever more crucial.

You build a tunnel to get people safely to the other side. The radio that works inside is part of that promise — not the part you skip.

Do you manage a tunnel or underground infrastructure and want to know whether the DAB+ coverage is up to scratch? Request a no-obligation coverage analysis — we'll measure it and show in black and white where the signal drops out.