By contrast, my moped horn gets attention of drivers in close proximity practically every time. It was a bit tricky to mount it so it sounded loud - a poor mounting could dampen the sound by a lot. I only use it on pedestrians when they have headphones on and I already exhausted the capabilities of my loud bell.
I think anything that closely sounds like an automobile horn like that of your moped horn will get drivers attention.
i was looking at my local hobby shop for lithium ion batteries we use to fly electric rc airplanes, looking to see what I can use for a 12 volt horn. A moped horn might be running of 6 volts so will look at that too. This will be my next step.