Burger King is planning to start a service that delivers its hamburgers to drivers stuck in traffic in Mexico City, Sao Paulo, Los Angeles and Shanghai.

The fast-food giant began a pilot program in Mexico City last month using an app that recognizes voice orders and uses real-time location to bring food to drivers in motion.

Gustavo Lauria, chief creative officer of We Believers, the ad agency responsible for the campaign, said Burger King is still refining the service proposal, including how to avoid some obvious traffic violations observed in the original ad, like navigating between lanes to hand the order to the driver.

Burger King will use Googles traffic reports to spot heavy jams and to set maps for navigation, Lauria said. One key issue is that the delivery has to be made within a 3-kilometer radius of the customer to guarantee that the burgers and fries arrive hot and that the beverages are cold.

The company has typically used the Rappi app, which employs bikers and motor bikers for deliveries of all sorts of products, to get its food to customers in several cities across Mexico.

Burger Kings new delivery service for some of the largest cities in the world comes as its owner, Restaurant Brands International Inc., struggles with results. Restaurants in many cities are experiencing less foot traffic and more online and mobile-ordered pickups.

Burger King Mexico general manager wasn’t immediately available for comment.