Horn

Not to be confused with Horn Deodorant.

The horn is a sound the player can cause a vehicle to emit for warning purposes. A horn is available for almost every land vehicle in the GTA series since Grand Theft Auto III.

Using the horn actually has no effect on traffic or pedestrians, but it is utilised in the mission Wear Flowers in Your Hair and used for friend activities in Grand Theft Auto IV.

Some horn sounds are shared between vehicles within the same game, whilst others are unique. In GTA IV, a severe crash to the front of the vehicle will often cause the horn to sound.

Sirens

Most Emergency Vehicles have sirens in addition to the horn. Holding the horn button will sound the regular vehicle horn, whilst tapping it will enable and disable the siren. Some vehicles also have a secondary siren noise sounded by holding the horn button whilst the siren is enabled.

Where fitted, flashing lights or lightbars also activate when a siren is sounded. A crash that affects the lightbar can cause the siren to not sound or sound incorrectly in GTA IV.