Metro

Barclays blastoff

Barclays Center opens tomorrow with the first in a series of eight concerts by rap mogul Jay-Z — and city, MTA and arena workers are working overtime to prepare for the mobs of people heading there.

The MTA on Monday opened its new $76 million subway entrance in the plaza of the 18,200-seat arena, providing swift access to the main entrance at Atlantic and Flatbush avenues. After the concerts, Nets games and other arena events, the agency says, it will add service on many of the 11 lines that stop there and will double LIRR service from Atlantic Terminal.

Fans planning to drive to the arena got good news Monday with the long-awaited reopening of the nearby Carlton Avenue Bridge, which closed for renovations in 2008.

Traffic agents and cops will be in full force near the arena to help ensure that pedestrian and vehicular traffic flow smoothly.