Google, part of Alphabet Inc, announced on Tuesday a new feature that will appear in the Google Maps mapping service this year. The service will begin to guide drivers along routes estimated to generate the lowest carbon emissions based on traffic, inclines and other factors.

Google said the feature will launch later this year, initially in the US, but will eventually expand to other countries as part of the company’s initiatives to tackle climate change through its services.

Unless users opt out, the default route will be considered “green” if comparable options take roughly the same travel time. If the alternatives involve significantly faster passage, Google will offer a choice and allow users to compare the estimated emissions.

“What we see is that for about half of the routes we can find a more sustainable option with little or no time difference,” Russell Dicker, director of product for Google, told reporters on Monday.

The company said it obtains relative emissions estimates by testing various types of vehicles and types of roads, based on data from the US Government’s National Renewable Energy Laboratory (NREL). Grade data comes from its Street View vehicles, as well as aerial and satellite imagery.

Google also noted that from June, the service will begin warning drivers about travel through low-emission regions, including Germany, France, the Netherlands, Spain and the United Kingdom, where certain types of vehicles are restricted.