The MTA apologized to customers Monday after a miscommunication about a tunnel construction project and a track error led to significant delays and frustrated customers along the D, N and R subway lines Monday morning.

The MTA began a structural rehabilitation project at tunnels in Brooklyn Monday - but it did not properly communicate those changes to riders beforehand, the agency said.

The agency says work on an approximately year-long project to repair and replace steel, concrete and tunnel lighting in the express tunnel between the 59th Street and 36th Street stations in Sunset Park began on Monday.

The repair work will cause N trains to make local stops at 45th Street and 53rd Street in both directions through at least July 2019, according to the MTA.

But according to NYC Transit Chief Customer Officer Sarah Meyer, the agency had "issues and challenges coordinating internally," and as a result, planned service changes were "not properly communicated to our customers."

With no advanced notice, riders were caught off guard.

(In a statement, Meyer said the blue wall is a construction barrier "which reduces our need to perform 'flagging' which slows trains down.")

Compounding the issue on Monday, Meyer said an error sending D trains onto express tracks at 36th Street caused significant delays along the D, N and R lines. That led to even more angry customers.

Riders on Twitter also said that while the trains they were on were severely delayed, those delays were not reflected on the MTA's website.

City Councilman Justin Brannan said he was one of those frustrated riders. He re-tweeted tweets from other frustrated riders and sent his own updates as well.
Eventually, Brannan got in touch with the MTA and tweeted about the service issue.
The MTA later put out a statement of its own explaining what happened.
 "We deeply apologize for our significant errors today and know that we need to do better," Meyer said in a statement.
The MTA added that Monday's delays "will not happen again," and they said the planned work will add "up to five minutes of additional travel time during the weekday rush hour periods going forward."