Due to the behind-schedule installation of station equipment and testing of critical components, the Second Avenue subway is facing more delays that could push back its opening, currently slated for December 2016.

On Monday, Kent Haggas, an independent engineer hired by the MTA to observe and report on the subway line's progress, told the MTA board that the project has fallen further behind schedule, Gothamist reported.

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"The project is not on schedule, has fallen further behind schedule" since June, Haggas was quoted by the Wall Street Journal. He claimed that 70 percent of the milestones related to the project had been met in June, which was lower than the 80 percent that were completed in May.

Haggas recommended to the MTA that a "revised schedule" be implemented if the project hopes to be completed on time, Gothamist added. MTA Chairman Tom Prendergast did not comment on Haggas' recommendation.

The latest delays were attributed to the production of elevator cabs for subway entrances, installation of communications equipment and the testing of a radio system for police, the Wall Street Journal added. The MTA also said it would push back prerevenue operations training by one month to Oct. 1.

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With an expected daily ridership of 200,000, the MTA has said the Second Avenue subway will relieve congestion on the 4, 5 and 6 lines, Gothamist stated.