I-95 North through the Baltimore tunnel. If I-95 traffic is very heavy, you can take the exit for Rt. 895 and go through the other tunnel which easily connects you back with I-95 North. Follow I-95 North through Maryland and into Delaware. Now you have a choice.
North is more direct, but goes through several cities.
Avoid it during commuting hours. 295 North through New Jersey is much quieter, and more rural. Both roads join North of Trenton where, either way, you exit onto Route 206 North to Princeton. I-95 North all the way through Wilmington, Chester, and Philadelphia. Go through the village of Lawrenceville and stay on Rt.