Thanks! Yeah, the horn will be actually functional. Not only for challenging other cars in Cruisin' mode, but also for something else:
I've programmed the AI cars, especially traffic cars to not swerve into your lane when they want to overtake someone. It's something that I don't like about other games, where they intentionally seem to do that. But my system isn't watertight. That's where the horn will come in handy. When they swerve into your lane, blast the horn and they should go back where they came from. At least that's the idea. :D Now I have to program it... And add the sound effect.