When did people start idling their cars?

There's no single date marking the start of car idling. It developed gradually with the invention and popularization of the automobile itself. As soon as cars had the ability to run without moving, people likely started idling them for various reasons, though it was probably less common in the early days due to:

* Less efficient engines: Early car engines were less fuel-efficient, making idling a more significant fuel waste.

* Technological limitations: Early cars might not have had the same sophisticated idle control systems as modern vehicles.

So, while pinpointing a specific start date is impossible, it's safe to say car idling began sometime in the early 20th century, shortly after the automobile became a common form of transportation. The practice likely increased as engine technology improved, making idling less fuel-intensive and more convenient.