Given the number of people (literally thousands) running down the roads with RV refrigerators running on propane, and the lack of accidents directly or indirectly attributable to the practice, I don't understand how anybody can say it is all that risky!
In all the various RVs I have owned over the years, I have always traveled with the propane ON and the frig operating. No incidents, accidents, or occurrences.
Here in the West I have never encountered a bridge or tunnel which required the propane to be turned off. I don't know if the Washington State Ferrys require the propane to be turned off or not, I don't take my RV on the ferry. Too expensive!