For a number of years there were actually 3 tracks through the tunnel. A Eastbound, Westbound and Gauntlet track down the center. Passenger trains could use both the Eastbound and Westbound, freight trains with equipment larger than AAR Plate B (standard cars) would use the Gauntlet track.
Needless to say passenger trains that used the tunnel made their station stop at the lower level of Camden Station. In addition to the CPL's at the entrance to the tunnel, in the early 50's (and probably long before) there was a 'Smashboard' that swung across the Gauntlet track when the Eastbound or Westbound tracks were in use.
In the early 70's only a single track was in the tunnel, down the center. It would clear open tri-level auto racks, 17'3" cars could run track speed of 25 MPH, 17'5" cars were restricted to 5 MPH account rocking and bouncing. Today the tunnel will clear 19'2" auto racks (all of which are enclosed) at track speed. The floor of the tunnel has been undercut to the level of bedrock. A pumping system has been installed to minimized flooding during periods of heavy rainfall.
The tunnel is the bottleneck to CSX handling double stack containers from the Sea Girt Marine Terminal & Dundalk Marine Terminal, both of which are on the East side of the tunnel and need to pass through the tunnel to reach the West. Double stack container are 20'2 inches high and 8'6" wide at that height.
Never too old to have a happy childhood!