NJ Transit has announced a bus service contingency plan in case the agency’s locomotive engineers go on strike May 16, as contract negotiations restart amid growing tensions between the two sides.

Kris Kolluri, president and CEO of NJ Transit, said he doesn’t want a strike but is preparing for one. Plans to enhance and expand bus service would cost the agency about $4 million a day — and even then it is expected to move only about 20% of those who use NJ Transit’s rail system.

“You can never replace the rails, one for one, with a bus system,” Kolluri said Wednesday at a press conference with reporters at the agency’s emergency operations center. “We are going to focus on moving essential workers who need to get to their work.”

“Those folks who can afford to work from home, should the strike become a reality, we ask them to work from home,” he said.