NEWARK, N.J. (AP) — New Jersey Transit says some trains have been canceled this week because engineers are choosing not to work under the terms of their contract amid the summer-long repair work at Penn Station.

NJ Transit spokeswoman Penny Bassett says about five trains were canceled Monday on the Coast Line and Northeast Corridor and an early morning North Jersey Coast Line train was canceled Tuesday because they didn't have crews to operate them.

NJ Transit also is using buses Tuesday for the Princeton Shuttle rail service following maintenance to overhead wires.

The track repairs and corresponding schedule cutbacks for commuters at New York City's Penn Station began last week. Amtrak is replacing aging signals and several thousand feet of track over a two-month period following two derailments and other problems.