"I have it confirmed from the U.S. EPA National Vehicle and Fuel Emissions Laboratory and the California Air Resources Board. There are tests that compare emissions over minute-long increments for restarted versus idled cars. I've seen the numbers for smog-forming nitrous oxide, poisonous carbon monoxide, chunky particulate matter, and volatile organic compounds. Idling produces more emissions. Over nine minutes, for example, an idling car will emit double the pollutants of a car that is turned off and then restarted. Of course, it depends on the car you're driving and other variables, but you can feel confident turning off your engine, unless you're the speediest pizza guy on the planet. If the delivery takes any longer than 60 seconds, you're doing everyone a clear favor.