Using the manual block, PATH is only serving about 30, 000 customers, Mr. Kingsberry said.

WSJ: PATH's Road Back Is Rocky

And it has required all hands on deck, said Kevin Lejda, assistant superintendent of the transportation division, who helped develop the plan to restore service using the manual block.

WSJ: PATH's Road Back Is Rocky

Trains are run on a similar, manual-block fashion on long, unsignaled sections of freight and passenger railroad in the country, so-called dark territory.

WSJ: PATH's Road Back Is Rocky

The so-called manual-block system takes the place of a dozen separate signals that help drivers adjust their speed and avoid colliding with other trains in the dark tunnels.

WSJ: PATH's Road Back Is Rocky