There's light at the end of the tunnel for the long-awaited Second Avenue Subway. 

Sources tell NY1 the MTA has switched on the power to the third rail for testing, marking a new milestone in the project.

Sources tell NY1 the third rails of both the uptown and downtown tracks got electricity on Thursday. 

According to a Transit Authority bulletin, workers powered up between 63rd and 95th Streets to ensure that it is "safe for service."

The MTA declined to comment on the test.

This comes as the agency rushes to begin service at new stations on 72nd, 86th and 96th streets beneath Second Avenue. 

The new line also will also serve the existing 63rd Street station between Lexington and Third avenues.

Officials have said the long-delayed line will open by the end of year.

A celebration is also being planned to mark the end of street-level construction along Second Avenue from 90th to 105th streets.