In the United States, McDonald's (NYSE: MCD) has reached a saturation point. The chain closed 2016 with 14,146 domestic locations, meaning that wherever you are, the Golden Arches probably aren't too far away.

In fact, while there are still countries where the chain has room to expand its footprint, many parts of the world have all the McDonald's locations they can support. That means that whatever growth it achieves will have to come from increasing its same-store sales.

For years, that seemed like it would be a difficult task, but now the fast-food giant actually has a tactic with real potential to increase comparable-store sales: delivery.

McDonald's has begun expanding its delivery locations. Image source: McDonald's.

What is McDonald's doing?

The fast-food segment has come to see delivery as a cure for the ills it has suffered due to the rise in popularity of fast-casual chains. It's not a solution that one would expect at first glance to work: Fast food doesn't travel well, making it a poor choice for delivery. But consumers seem to prize convenience over everything else.

That partly explains the ongoing success of Domino's (NYSE: DPZ), a company that has perfected the art of rapidly delivering mediocre pizza. The chain has made it incredibly easy to order and have its food delivered. That's the model McDonald's is following.

"Over the course of the past nine months, we've introduced delivery in over 5,000 restaurants across 20 countries," CEO Steve Easterbrook said during the chain's Q3 earnings call. "Along with the 3,500 restaurants in existing delivery markets across Asia and the Middle East, we now offer delivery in over 20% of McDonald's restaurants around the world."

Easterbrook expects McDonald's will offer delivery in 10,000 locations when 2017 ends. That's slightly over 25% of its nearly 37,000 restaurants worldwide. It planned to offer delivery in 5,000 U.S. restaurants by 2018.

Why is this important?

Delivery can lead to increased revenues. The chain has not provided hard data on this, but Easterbrook said during the Q2 earnings call that delivery led to "higher average checks." The potential for that to grow revenue across the chain is significant, given that the CEO noted that 75% of the population in the company's top markets lives within three miles of a McDonald's.

"In many of our markets around the world, we're seeing average check sizes between 1.5 and 2 times higher than our overall restaurant averages," he said.