The car horn is a rather jarring and unpleasant sound. Not the kind of thing you want ringing your ears every so often. But it does have its uses. For example, if the car in front of your vehicle is slipping backwards on an incline due to improper application of brakes, and looks like it’ll hit your vehicle soon if you don’t take action, then lean on your horn to alert the driver of said car to the situation. Fair use of the horn, in my book. If someone is trying to cut dangerously into your path and you think you can’t brake fast enough to avoid colliding with him if he actually does cut in, then honk at him to try to alert him to the danger of the situation. In short, any use of the horn in which you are alerting another road user of an impending collision is fair use.
What the Horn Is Not
It is not an outlet with which you vent negative emotions like frustration, anger, impatience, annoyance, etc. Leaning on your horn because you are annoyed about being stuck in a traffic jam will not resolve matters. Everyone in the jam is annoyed by the traffic jam. No one is creating or exacerbating the jam on purpose. Your leaning on your horn during the jam is not going to cause anyone to stop jam-exacerbating behaviour. Honking at road users whom you are annoyed with does not help either. As I said, the car honk is a rather jarring sound. It does cause people to literally jump in their seats if deployed at close quarters. So if you are passing another road user at close quarters, and you are annoyed with that person for some reason, and wish to transmit that annoyance by honking as you pass that person, you may risk causing an accident. For road users that jump in their seats temporarily lose concentration and control of their vehicle. You don’t want your shiny paint to be scratched by a pathetic bicycle, do you? Then don’t make cyclists jump by honking as you pass them. The horn is an instrument to alert other road users of imminent danger that could be avoided. It is not an instrument with which you use to create otherwise non-existent dangers. From this, you may also infer that honking at cyclists because you don’t have enough room to pass them even though they are already as close to the curb as is safe is not fair use of the horn. This may be hard to believe, but cycling close to the curb requires concentration. If you honk at them when they are already doing so, they are likely to momentarily jerk a little away from the curb, simply out of sheer shock. This will not help you to pass them. It may cause them to crash into you if you’re already breathing down their necks. Guess what. We expect to be passed. If you think you can pass, then pass, and pass quietly. If you think you can’t pass, wait quietly. Honking when we’re already fully compliant about keeping left is equivalent (and perhaps this is the intended meaning) to you yelling “get on the sidewalk!” to us.
I apologise for inadvertently switching pronouns mid-paragraph again.