A 25 mph speed limit is unrealistic on any public road I've ever seen, with the exception of roads made of cobblestone. It's difficult to drive a modern vehicle that slowly--it takes concentration on your speed that frankly makes you have much less attention to pay to obstacles and hazards... like children.
Odd. My car drives at about that speed idling in third gear. It takes no effort at all. If I want a slower speed I pick a lower gear. It is a high volume production car with no mods.