From 1995 to around 2007-08, the
Lantana Toll Plaza on the southbound side of Florida's Turnpike was 12 lanes wide, back in the days before the concrete barriers separating the dedicated SunPass lanes. That's probably the single widest slab I've driven on which wasn't an abandoned airstrip.
Hmmm...looks like the NJTP toll plaza for the George Washington Bridge is at least 15 lanes in one direction!
Been on NJTP by I-95, 401 in Toronto, I-395 and I-95 south of Washington, but I don't think I've driven by the Pentagon example.