I think at least some tunnels don't allow fuel trucks.
In LA, there is a tunnel for cars right under the LAX airport and there are posted signs saying that no trucks allowed, but if the terrorists decide to step on the gas pedal, how are they going to stop them?
Good question.
We have two tunnels here under Mobile Bay and one of them is I-10 but, we are small fry compared to other potential high profile targets. I would be guarding the Holland Tunnel, they had plans once to 'hit' it but were caught before succeeding.