Car MOT Manual 2012 onwards
Lamps, Reflectors and Electrical Equipment - 1.6 Audible Warning Horn
2. Operate the horn and note the volume and character of the sound emitted
Note: Inform the driver if the horn is insecure.
2. The horn:
b. is not loud enough to be heard by another road user
c. is a gong, bell or siren
d. has more than one tone
Note: When operated, a two or more tone horn automatically produces a sound which alternates at regular intervals between fixed notes.
e. fitted to a vehicle first used on or after
1 August 1973, emits a sound which is:
• not a continuous or uniform note
• harsh or grating.