Idling: more pollution or not? Government study, modeling

[masscommuter]

Seeking feedback ! re govt. studies on pollution from idling enginerestart

Having huge debate w/ a friend re a bumper sticker:
No Idling: I turn my engine off when not needed.
He laughed derisively at it - - says a government study proves more particulate exits the exhaust at startup due to "sloshback" in the engine/ exhaust system.

so - due to re-start, no-idling philosophy = more pollution.

I'm highly skeptical.
a) Any federal govt study in last 8 years would have serious industry bias,
i.e., bought & paid for by Detroit.

b) A warmed-up engine's startup clearly produces less pollution,
more complete burn, less "bypass" of worn rings etc.

Does anyone know of Govt. studies on this?
Thanks to any & all for followups.

[satchel]

Whenever I see idling mentioned I think of the farmer who left his truck running for over an hour and a half outside an implement dealer I was auditing. All I could think was how far I could have driven on that fuel wasted. Or that what he used driving into town would have likely gotten me 120 miles home! I'm resigned to thinking that's where all I save ends up going. All our conservation might harvest a hill of beans, so to speak.
In the larger scheme of things I mention my mileage to my jet jockying nephew and he says he measures fuel consumption in gallons per mile!

[magus_melchior]

I'm inclined to think that whatever study your friend is referring to either doesn't reach that conclusion, or doesn't exist.

[JimJohnD]

I found this:

EPA School Bus Study Shows Idling Worse Than Re-starting Engines
05/21/2007: EPA School Bus Study Shows Idling Worse Than Re-starting Engines