Bus countdown clocks will be installed at 350 additional stops around the city, Mayor Bill de Blasio will announce on Thursday, as part of a larger strategy to speed up buses citywide, including new bus-only traffic lanes.

The clocks utilize data from MTA’s BusTime system, which uses GPS to track where buses are. Riders at stops without them now have to use a cell phone to check how far away the bus is.

The City Council allocated money for about 250 bus countdown clocks over the past two years, but only three countdown clocks have been installed so far on regular bus routes. There are also 29 clocks on select bus routes, where riders swipe their MetroCards before getting on.

The leftover City Council money, combined with an infusion of cash from City Hall, will fund the 350 new clocks. Installation will begin immediately and wrap up next year. Additional clocks could also be funded.

New York has the highest bus ridership of any city in the U.S., at about 2 million a day, but city officials say its buses are the slowest — due to traffic jams and the long times it takes riders to board.

To get buses moving quickly, the city will add traffic signal technology to eight routes by 2017. They will also add new bus-only  lanes.

For the traffic signals, a green light will stay green longer if a bus is approaching, and a red light will go green sooner if a bus is waiting. The MTA Bus Command Center communicates with the DOT’s Traffic Management Center through a transponder on the buses.

Routes that will get this new technology include Main Street in Queens, Victory Boulevard in Staten Island and Kings Highway in Brooklyn. It’s not clear where the bus-only lanes will be added.

“While we never want to wait for anything, 350 more countdown clocks will mean real-time information and less hassle,” said Mayor Bill de Blasio, who will formally announce the bus plan in his state of the city speech, in a statement.“Combined with our efforts to further speed up bus service around the five boroughs, we’re focused on utilizing new technology to improve quality of life for New Yorkers.”

The Riders Alliance, an advocacy group that has been pushing for the clocks, says they are particularly helpful for senior citizens and low-income riders, who use buses disproportionately and may not have access to a cell phone or data plan.

“These clocks turn buses into a modern and convenient option for riders,” said John Raskin, the executive director of the Riders Alliance. “There’s nothing lonelier than standing at a bus stop wondering if the bus is ever going to show up.”

At Manhattan’s only bus countdown clock, on Broadway and Barclays Street, some riders from the x1, x17 and x19 bus lines said the sign was glitchy. They use the MTA’s BusTime service on their phone instead.

“The sign doesn’t always work,” said David Tricario, 42, of Richmondtown in Staten Island. “I’m using the MTA app now, it’s really good.”

Others liked having the sign there. “I think this is more convenient than the app,” said computer programmer Slava Roben, 43, from Staten Island’s South Beach neighborhood.

The borough’s councilman, Steven Matteo, who represents mid-island neighborhoods, said there had originally been enough money for 10 countdown clocks. The new money could allow him to double the number.

“On Staten Island, in particular, where buses are the primary source of public transportation, these devices will make it just a bit easier to travel,” he said.

In Queens, councilwoman Julissa Ferreras-Copeland said the countdown clocks would be a boon to travelers on buses that connect with airports.

“Countdown clocks will be particularly useful in my district on the routes that take visitors, airport workers and residents to and from LaGuardia Airport,” she said.