In the interest of rider safety, NJT made the call to test the wheels of all 19 cars in the River Line fleet.
Agency spokesman Jim Smith says 14 of them have passed the inspections, and the rest are to be tested this week.
"The safety inspections are continuing," Smith said.
After the remaining five cars pass inspections, they will be returned to the fleet.
A dozen cars are running Monday, which is less than usual, so express shuttle buses will be rolling again, making stops at the four busiest River Line stations between Camden and Trenton.
"The shuttle bus will offer our customers an additional travel flexibility in case there are capacity issues," Smith said.
Buses will run every 30 minutes during the morning and aftenroon rush.