Garbage out of a car window!

On my way back home today, was trailing a shiny new Innova with white shirt-dhoti types inside - near the Aiyappa Temple just before Agara Juntcion. Looked pretty decent until one of them rolled down the window and smack...flew a banana peel outside splat on the road. How I really wished I could tell them something. Not angrily of course, since that beats the purpose and is bound to get into a 'who-are-you-to-tell-me-that?' loop.

Was wondering if we can come up with a more subtle but effective way to tell such folks the kind of nuisance they are causing. How about a simple placard (to be kept handy) and fit it to the window as you try and drive adjacent/ past these folks?

Would that distract you from driving? Is that manageable? We could look at having a simple sentence, "Please do not throw garbage on the road out of your car. PLEASE!" fixed on the back of the sun-control vinyl boards with that suction pads...those things that you get in traffic signals. So, when you see someone treating Bangalore roads like a dustbin, just pick up this thing and stick to your driver-side window till you pass these blokes. How does that sound?

Given some feedback/ momentum, I can try and get a vendor to brand these messages and give it out as a gift to random people.