The union that represents the engineers who drive New Jersey Transit’s commuter trains has threatened a walkout as soon as Friday if a contract deal is not reached.

Transit agencies across the region are rolling out emergency plans as a possible NJ Transit rail strike threatens to disrupt service for riders starting Friday.

For months, officials at the rail agency and the NJ Transit Brotherhood of Locomotive Engineers and Trainmen have been locked in tense negotiations over pay raises for the roughly 500 transit workers represented by the union.