Beep Beep

I almost find it ridiculous that in this day and age, a new car still only has one beep sound for it's horn. A sound that is supposed to convey numerous messages to fellow road users, from 'Cheers mate!' and 'look out, I'm approaching the corner' to 'Get the fuck out of my way! This is my road!' ...and everything in between.  The only current difference between all of the above, is the length of the beeeep.

Cars should have more than one horn sound.

I'm not suggesting that you have a great myriad of polyphonic sounds, just three or four alternative beep sounds, which better articulate the sentiment you're going for.
For example, for a simple 'Thank you' noise, you're going to want a lighter meep-meep sound  - not too dissimilar to the horn on Postman Pat's van. You know the one. Everybody knows his bright red van. So Pat's got that one sorted already, but what if he's in a pile up? What if Ted's truck's broken down, and Pat's got an urgent delivery for the vicar? He's gonna want the extra aggressive grunt in his beep. If only to help him let of a little steam. Unfortunately he's only got that little 'meep' horn; It doesn't really do the trick when what he really wants to say is 'Yo momma!' to Ted Glenn.
This could have also been a contributing factor for Post Office workers who have been known to 'go postal'. Despite the inadequacies of Pat's van, it has been recorded for the record that he feels he's a really happy man. Mind you, that was before news of the Royal Mail's impending privatisation.

The multi-horned car is an idea I came up with many years ago. In the interim I've heard one or two other people mention the same idea to me independently. I definitely thought if it first though. Oh, what's that? You came up with the idea too? ...When was that?...  Oh really? Well I thought of it about five years before then.