No ground motor vehicle should be left unattended with its motor running unless which condition is true?

A ground motor vehicle should not be left unattended with its motor running except under specific conditions that prioritize safety and operational efficiency. When weather or operational conditions dictate otherwise, it implies that there are exceptional circumstances that make it necessary to keep the vehicle running. For instance, in extremely cold weather, keeping the engine running may be essential to prevent freezing of vital systems or to maintain passenger comfort and safety.

This consideration recognizes that there are instances where operational needs or severe weather conditions override the general rule of not leaving a vehicle unattended with the engine running. It's important to ensure that the vehicle does not pose a risk of theft, accidents, or environmental hazards, but in certain extreme conditions, there might be justification for this practice.