SEPTA will resume regular weekday regional rail service starting on Monday following months of disruptions and emergency repairs to some of its damaged rail cars.

The transit authority has been operating since July with limited capacity after inspectors discovered structural cracks on about one third of its regional rail fleet.

On Monday, more than 50 repaired trains will be available for service. Officials sidelined 120 when the widespread defect was discovered. 

The repaired train cars, along with other rail cars SEPTA is now leasing from other transit agencies, will bring schedules back to normal, though SEPTA Spokeswoman Carla Showell-Lee said some bumps along the way should be anticipated. 

"Remember, as we bring in new cars, on the back end, we're still servicing our older fleet that's been running constantly, so we have to do some inspections of those cars, too, so it's going to be a little give and take," she said.

After a SEPTA inspector noticed cracks in the equalizer beams, a part that stabilizes the axles of the rail cars, the 120 Silverliner V cars were taken out of service for emergency work. 

SEPTA officials attributed the cracks to a poorly designed weld that was connected to the equalizer beam, a flaw that worsened with time and eventually formed cracks.

After conducting stress tests that simulate the impact of 40 years of service, SEPTA began replacing the parts and installing new stabilizing beams that address the design flaw that caused the cracks.

Starting Monday, passengers should refer to schedules dated June 19, 2016, for the most updated arrival and departure time information.

There are some exceptions, however.

The Media/Elwyn Line had been modified because of summer construction and will have a new schedule starting Sunday. In addition, four of SEPTA's leased trains coming and leaving Center City will experience some schedule modifications. Details about those trip changes can be found here.

The financial blow to SEPTA has been significant.

SEPTA estimates that rider refunds, leasing cars from other transit agencies, hiring engineering consultants and paying workers overtime has added up fast to $7.8 million, a cost expected to climb as leasing and repairs continue. 

Showell-Lee said the worst appears to be behind the transit agency. 

"People who have complained, and you know, they're angry with SEPTA right now," Showell-Lee said. "We just want to thank them for sticking with us. We know it's been rough out there."

Meanwhile, ridership plummeted by 20 percent from the same time last year, but transit officials are hoping that restored service will help bring back those commuters. 

"What people have done is gotten on other trains, or gone to another station and ridden into the city," Showell-Lee said. "We're hopeful that when the new schedules resume, people will get in the habit of what they used to do."