New Jersey faces a possible transit strike. Here’s what you need to know.

Hundreds of thousands of New Jersey commuters could be taken in the first state strike in more than 40 years from Friday morning.

The engineers who drive the suburban trains of New Jersey Transit threatened to go out after midnight Thursday if the union which represents them cannot reach an agreement with the agency on a contract which has been negotiating for several months.

The engineers said they were looking for parity in terms of wages with engineers in other suburbs in the region. The director general of the transit agency, Kris Kolluri, said on several occasions that he could not afford the increase in salary that the union was demanding.

The two parties met the National Mediation Board in Washington on Monday in a last effort to resolve their differences. Mr. Kolluri said the discussion was “constructive” and that he was eager to continue the negotiations in good faith.

In the meantime, New Jersey Transit has developed an emergency plan. But Mr. Kolluri said that the additional buses he would offer as a substitute in the event of a strike could only manage 20% of daily riders.

The agency asked commuters to make plans to work at home if their presence at the workplace is not essential. Kolluri said a strike could last for weeks.