small carbon footprint

Evan: "Sometimes I take the kid taxi. Kids have their own taxi service, you know."

Eric: "I didn't know that. ... So, who drives the taxis?"

Evan: "Kids do. But the cars are smaller than regular cars."

Eric: "Oh. Do they drive on the sidewalks?"

Evan: "No, they drive in the streets. But they have flashing lights and sirens, and signs that say, "LOOK OUT. I'M DOWN HERE."