Each tunnel has its own regulations, so there is not single answer. Most open highway tunnels have no restrictions at all, but those under rivers and bays often have LP restrictions because leaky LP could accumulate in the low spot near the middle.
So, what tunnels will you encounter on your route? If you are talking about the PA Turnpike tunnels, I do not believe there are any restrictions on LP gas in non-bulk quantities.
2004 American Tradition; 2014 Buick LaCRosse
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