SEPTA has a big summer construction schedule. Here’s what you should know.

Orange barrels and cones are blooming on roads and highways throughout the Philadelphia region, a reliable sign that summer, the construction season, is here.

Public transit systems like to use the usually slower summertime for substantial construction and repair work in hopes of minimizing disruptions — but SEPTA’s three big projects, scheduled for July and August, seem sure to inconvenience some riders despite the transit agency’s detailed plans to use buses and other alternatives to move people around the work zones.

The biggest? A complete shutdown of the Center City trolley tunnel for more than two weeks, from July 8 at 10 p.m. until July 25 at 5 a.m. for the 10th annual “blitz” of heavy maintenance and construction in the 80-year-old tunnel.

Customers who use Regional Rail’s Fox Chase Line, with service to Center City, will be bused from the Fox Chase Station to the Wayne Junction Station in Germantown from July 5 through July 29 as workers rebuild track and make other upgrades to that section.

And service on three Regional Rail lines — Media-Elwyn, Airport, and Wilmington — will be interrupted between 30th Street Station and University City on five weekends in July and August for upgrades to signal and switching equipment.

Here’s more information on the projects and how to navigate around the work:

Normally, SEPTA schedules maintenance for five hours on Sunday and Monday nights but the blitz is designed to get at more extensive repairs and improvements in the trolley tunnel that runs from 13th Street to 40th Street without interruptions.

“We run around the clock for a 16-day window,” said Dave Montvydas, chief engineer for SEPTA’s Engineering, Maintenance and Construction Division. About 200 day-shift workers and about 150 workers on the night shift will swarm the tunnel, he said.

Workers will demolish and rebuild the entire eastbound 22nd Street platform, and replace the track bed there. They also will replace worn track at curves throughout the tunnel; install four miles of new overhead wire that powers the trolleys; clean and flush pipes and drains; repair switching equipment and test and maintain signals.

Trolley stations in the tunnel are scheduled for deep cleaning, repairs, and repainting. Workers will be repairing some spall, or crumbling concrete, on the tunnel and checking for any other signs of damage, said Kate O’Connor, the chief engineer for buildings and bridges.

Workaround: Trolley Routes 10,11,13, 34 and 36 will drive to 40th and Market Streets during the blitz. Customers can transfer there to the Market-Frankford Line for Center City, and do the reverse from 13th Street, SEPTA officials say. Tents will shelter people transferring between the El and the trolleys.

For late-night travel, customers can take the Night Owl Bus Service that parallels the route of the MFL.

The Fox Chase Regional Rail Line will be shut down from Fox Chase to Wayne Junction between July 5 and July 29. Wood railroad ties will be replaced, track resurfaced, and concrete poles for overhead wires installed. Overgrown vegetation along the line will be cleared.

“The tie replacement and resurfacing will provide for a smoother, more reliable ride,” Montvydas said. “There’ll be better drainage.”

That gives an opening for workers to fix up a bridge that SEPTA shares with CSX, a freight railroad company.

“When the tracks are out, we’ll do any repairs that are necessary on the concrete below and then install waterproofing before they put the tracks and pads back in,” O’Connor said. The abutments and steel will also get repaired, she said.

Shuttle buses will replace all trains between Fox Chase and Wayne Junction stations, with train service from there into Center City.

This $80 million project to upgrade switches and signals, or interlockings, on Regional Rail track between 30th Street Station and University City is now in its fifth year. Because of supply chain issues that made it hard to get the large huts needed to house computer and electronic equipment, and difficulty scheduling a crane, 18 days of work will be spread out over about six weeks, officials said.

“What we have out there now is at the end of its useful life, and it’s time to replace it,” Montvydas said.

The work is scheduled over several weekends: July 9-10; 16-17; and 23-24; Aug. 6-7, 13-14 and 20. The line will also be shut completely from Aug. 15 to 19.

SEPTA plans to use a combination of shuttle buses and to run Wilmington and Airport line trains at a reduced schedule, arriving and departing on the lower level of 30th Street Station.

The authority will also have signs and people to help flummoxed passengers there, at Fox Chase Station and on either side of the trolley tunnel.