CHICAGO (CBS) — Metra is making an effort to alleviate the overcrowded trains some riders have been dealing with since new schedules went into effect on the BNSF Railway line on Monday.

Some BNSF trains have been so crowded during the morning rush this week, Metra issued a letter of apology, and decided to add extra cars to a half dozen trains beginning Wednesday morning.

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“Barring any unforeseen changes, BNSF will be adding another car to the following inbound trains for morning rush to help with crowding: 1202, 1210, 1226, 1230, 1244, 1262,” Metra tweeted Tuesday afternoon.

The crowded trains were the result of a schedule change Metra needed to make on the BNSF line after installing positive train control train safety systems, designed to stop trains automatically to avoid a collision or derailment if an engineer fails to do so.

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PTC technology adds 12 to 15 minutes to the time needed to get an arriving train ready for the next departure, meaning longer turnaround times that required Metra to shift BNSF schedules.

The new schedules led to significant overcrowding on many trains Monday and Tuesday.

“I’ve got to get up earlier, or leave later, and I notice the train’s much crowded. So it’s kind of hard to find a seat sometimes,” Metra commuter Jacob Cullinan said.

Fellow commuter Bonnie Jean Adams said, normally taking an earlier train in the morning meant more open seats.

“Now, no matter what train you take, you’re standing room only,” she said.

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The BNSF Railway is the first of 11 Metra lines to use PTC. All of the lines are expected to use Positive Train Control by the end of 2019.