All underground Metro stations will offer free customer Wi-Fi starting Friday.

The service, which was first piloted in August 2016 in downtown D.C., will also expand to above-ground stations by the end of 2018. Customers can access the network by connecting to “Metro-Public,” the Washington Metropolitan Area Transit Authority announced in a release Thursday.

The Foggy Bottom station began offering free Wi-Fi to customers in December.

“We are always looking for new ways to improve safety and the customer experience on Metro,” Metro General Manager and CEO Paul Wiedefeld said in the release. “Providing free Wi-Fi access at all 91 Metrorail stations will help customers stay better connected while they travel.”

Metro also joined the nation’s four largest wireless carriers — AT&T, Sprint, T-Mobile and Verizon — to expand cellular voice and data access to a new section of the Blue and Silver lines. Riders will now be able to call and surf the web from Metro Center to Largo Town Center uninterrupted, according to the release.

Approximately one-third of Metro tunnels currently have service, but work is underway to extend cell service to all tunnel segments, the release states.