Friday marked the beginning of a summer of slowdowns for PATCO high speed line commuters. A major track replacement program will mean delays of a half hour for some riders.

The $1.86 billion project to replace worn-out infrastructure is long overdue, said John Hanson, PATCO president. The first phase will involve the tracks on the south side of the Ben Franklin Bridge.

"There's going to be a 60-day outage where we remove the entire track system, that is the manual system that we are going to take out," he said. "That's the ties and the rail that the trains run on, so we are going to remove that and replace that."

To move the trains as smoothly as possible during the project, Hanson said PATCO is going to run all its trains from one end of the line to the other -- and then move the empty trains back and do it all over again.

The net result will be an abbreviated schedule with more delays than normal.

WHYY's director of digital news Don Henry,  a daily PATCO commuter, said he hasn't seen panic on the platforms, but that a number of riders Friday seemed upset with the change in their everyday routine.

"There were a lot of disgruntled people ... the platform was absolutely jammed," he said. "The train was as busy as I've ever seen it, but people were really good natured about it."

Martin Kelley live-tweeted his experience on day one of the repairs.  He said he was pleasantly surprised with how helpful PATCO workers were.

"They weren't on Twitter ... a lot of us like to complain on Twitter," Kelley said. "I thought they were quiet there, but it looked like they were spending their time actually on the platforms."

The big test will be how things progress over phase one, which is expected to take two months. Commuters face another two months of delays after that for the duration of work on the bridge's north side.

PATCO officals advise commuters to consult the new schedules posted online and available at stations to avoid delays on trips between Philadelphia and South Jersey.