Since July 2019, it has been mandatory to install a warning sound generator in electric cars. This is due to a new EU Directive. This stipulates that initially in newly certificated hybrid, electric and fuel cell vehicles - also trucks and buses - the Acoustic Vehicle Alerting System (AVAS) must be installed for the protection of other road users. In the EU the acoustic warning is mandatory up to a speed of 20 km/h. The Directive formulates the parameters for how an AVAS warning may and may not sound in great detail. This applies for example to the minimum and maximum sound volume, and to certain sound components.

The Mercedes-Benz AVAS sound differs only slightly for the EU, Japan and China. There are other requirements for the USA, for example concerning the sound volume. Furthermore, the stationary vehicle must already generate a sound when a gear is engaged, becoming louder up to 30 km/h. Switching off the AVAS by the customer is prohibited in almost all countries.