re: "That's why it's probably best to just ask a traffic cop or two... "
...or three or four or more.
Being in a business where I have to call customer service organizations at a large number of different companies, I am very well tuned into the fact that 1 or even 2 calls isn't usually enough to get the right answer. Sometimes one rep is just plain wrong and other times a more savvy one will be a bit more creative is dealing with the issue.
When we start dealing with individuals such as police officers who not only have to deal with law but also have some leeway in how they apply it, I doubt you could get a 100% correct answer that you could rely on when the situation actually came up.
"But Officer Friendly said I could use a Suicide Knob. Why are you giving me a ticket?"
"I'm not Officer Friendly."