Today, I walked from Tottenham Court Road to the St Margaret’s Street blood doning centre and through the back streets I happen to pass a chap in a jeep with his engine running. He was tapping on his mobile phone with the window open.
I whipped out a leaflet and simply said: “Hello. I represent a local initiative. Can I give you some information?”. He took the leaflet and immediately recognized the problem, said “oh! yes” and switched off his engine. He looked embarrassed but I smiled and said thank you and walked away.
I realize that the most effective way is simply to offer the information without any explanation.