NEW YORK (PIX11) -- Transit improvements can bring delays and service changes for commuters as construction gets underway.

But a big project along the tracks in East Harlem is changing the workflow.

Passengers may have noticed work along the Metro-North track after leaving Grand Central.

Big yellow machines on wheels known as gantries line the Park Avenue viaduct in East Harlem. Crews are transforming the 130-year-old track and steel structure without interrupting train service.

"It's better because it’s less inconvenient to the passengers," said Sonia, a commuter waiting for a northbound train.

The viaduct has been replaced from East 115th Street to East 123rd Street, and MTA officials, planners, and workers marked the end of Phase One at the job site on Monday.

MTA Chairman Janno L

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