A mostly Philly question about double stacks

Sorry to annoy the outlanders, but I can’t stand not knowing the answer any longer.

My daily commute takes me along the infamous Schuylkill Expressway, which roughly parallels the ex-Reading main out of Philadelphia, now NS and CSX.
Just outside Philadelphia is the well-known Flat Rock tunnel. Time after time, I see a train with double-stacks stopped at the signal about 75 yds. east of the bore. I look at the size of the bore, and I look at the stacks, and I say, “no way.” But never in all my months of commuting have I ever seen the train actually going through the tunnel.
My question(s): Is there a standard height for double-stacked containers on cars? And does anybody happen to know the clearance of the Flat Rock?
Stopping my car on the expressway to wait for the trains to move is not an attractive option. Maybe NS/CSX are just really slow learners, and each of those trains have had a “oh, darn” moment and turned back just i8n the nick of gtime.

Two “tall” boxes will come out to 20’2". Flat Rock was undercut to handle them in the early 90s - at the same time as the tunnel work in Gallitzin was done as part of the overall clearance project partially funded by the state. The reason the state chipped in the money was to keep Philly a competitive port.

Don,
Thanks for the response. I remember the state project, but if I ever knew that Flat Rock was a part of it, I had forgotten.
I still will not believe, however, that 20’ stacks really do go through that tunnel until I see one.

Larry- A good clue would be to look around the tunnel entrance for things that look like the peeled back tops of sardine cans, only larger. [:D][:D]

Jay

Well, I am convinced that the reason I always see the trains stopped is that they are coating the container tops with grease.