What the Experts Say

(The) congestion that occurs in the parking lot, together with the start-up emissions and emissions from the extra travel distance to get to and from a space, all contribute to produce somewhat higher emissions per vehicle compared to a store that has a drive-thru. RWDI study
Mike Lepage, M.Sc., CCM
Principal / Project Director
RWDI AIR Inc.
There are no emissions benefits being realized by the current ban on drive-thrus windows at either existing or new convenience restaurants. In fact, there is likely to be a slight decrease in emissions of all pollutants if the current ban on drive-thru windows is eliminated.
Sierra Research
Sierra Research:
Analysis of the Effect on Emissions of Allowing Drive-Thru Service Lanes
From these tests on modern vehicles, it is concluded that there is little impact on emissions due to the choice between idling or engine shut down when the vehicle is stopped for duration between 10 seconds and 10 minutes. GW Taylor Report

GW Taylor Consulting