A. To warn another driver of your presence
A. To warn another driver of your presence
B. To warn a horse and rider you are approaching
C. If someone cuts you off
D. As you are leaving your friend's house
A reasonable traffic warning is where you need to warn a driver to prevent them from doing something dangerous, not to reprimand them for doing something dangerous.
For example, if a pedestrian starts to cross the road because they haven't seen you, you would be justified in using your horn. Using your horn to attract the attention of a pedestrian you know on the side of the road isn't a valid use.
You should only use your horn for an emergency between 11pm and 7am when in an urban zone (50kph area)
You should never use your horn around horses with riders, as they can bolt. However, if there's a dog or cat on the road and you are at risk of hitting them, use your horn.
Motorbikes may feel the need to use their horn when travelling around heavy vehicles as it's easier to be in the driver's blind spot. Good road positioning can minimise the need to do this.