The average gas mileage m in miles per gallon for a compact car is modeled by m(s) = -0.015(s - 47)^2 + 33, where s is the car's speed in miles per hour. The average gas mileage for an SUV is modeled by m(s) = -0.015(s - 47)^2 + 15. What kind of transformation describes this change, and what does this transformation mean?