In case of an emergency, the Voice Evacuation System needs to guide people in the tunnel to safety so the audio transmis-sion should be as clear as possible. In general, due to high levels of reverberation and noise, a tunnel is not an ideal environment for Voice Evacuation System and therefore speech intelligibility becomes a critical parameter for any voice alarm application. To establish a sufficient level of speech intelligibility, a highly directional speakers system is required. By reducing the energy emitted to other surfaces, reflective sound energy can be minimized which results in a better direct to reverberant ratio. This will improve the maximum feasible speech intelligibility. To minimize disturbing echo effects, resulting in a loss of speech intel-ligibility, each horn speaker is driven by an individual signal channel in a 100 V installation, which is equipped with audio DSP inclu ding EQ and delay. Our product S4T (Safety For Tunnel) offers the most effective solution which seamlessly combines a dedi-cated Voice Evacuation System with tailored Tunnel Loudspeakers.