That means no sitting in a parked car or waiting in a line of cars with your engine running for more than 3 minutes.
The Vice Mayor of Palo Alto says it would make the city a healthier place by reducing pollutants in the air.
"You'll be safe here. You can breathe easily," said Vice Mayor Liz Kniss.
Kniss also said the state already has a 3 minute rule for trucks and buses. But, Palo Alto would be taking it a step further and applying the rule to everything with a motor.
She said the practice of idling is most evident at schools and sports fields where parents are waiting to pick up their kids.
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