You are going to work in your car. On the way, you stop at a red trafic light. And then, people come up with bottle of so called cleading product and a scrapper, and offer you to clean (or, more accurately, dirty) your windshield for a coin.
Congratulations! You just fell prey to a Trafic Light Ambush.
This trope is not restricted to windshield "cleaners", but also include all similar panhandling (Selling flowers at the trafic lights...)
- You probably already encountered them.