A speaker addresses a "sir" who is having old trees cut down so that cars can pass more comfortably. The speaker is quietly angry, but the anger comes through pointed repetition rather than shouting. "You wouldn't know, sir" returns again and again, suggesting that the man in power has never bothered to look at what he is destroying.
The speaker remembers walking under these trees for forty years, and also remembers the people who depended on them: small sellers, tired old people wiping their faces, and animals and birds. The poem treats the shade as a shared place where the overlooked could rest, not just as scenery.
The mood moves from gentle memory to sharp accusation. The ending turns the heat into a warning: one day, the speaker says, "everything comes to a halt," and the comfortable driver will feel what the shade once softened. The last question, "Where is your car going, sir?", leaves the reader wondering what this kind of progress is really for.