  Google Maps uses current and historical traffic trends to provide routes to
drivers. In this paper, we use microscopic traffic simulation to quantify the
improvements to both travel time and CO$_2$ emissions from Google Maps
real-time navigation. A case study in Salt Lake City shows that Google Maps
users are, on average, saving 1.7% of CO$_2$ emissions and 6.5% travel time. If
we restrict to the users for which Google Maps finds a different route than
their original route, the average savings are 3.4% of CO$_2$ emissions and
12.5% of travel time. These results are based on traffic conditions observed
during the Covid-19 pandemic. As congestion gradually builds back up to
pre-pandemic levels, it is expected to lead to even greater savings in
emissions.
