You need to know why.
Sometimes it is because they want to control the flow of heavy truck traffic through town, and the route still carries moving vans, garbage trucks, school buses, dump trucks on local construction, et al. Other times it is because there is a 5-ton bridge, or an 8-foot overhead clearance.
In my RV, only 7 tons fully loaded and good for 12-foot clearance, when I come to a strange town and there is a truck route, other streets no trucks allowed, I will follow the truck route, because the reason might be that 8-foot clearance.
Between the highway and my house, the roads are marked "No trucks over 7 tons empty." I can't go on any just street in that area, but I do know which streets I can use to get to and from my driveway. And my RV is not over 7 tons empty, and it is not a truck. It was about three tons empty, but it is full carrying a four ton house (or so I will argue in traffic court, should it come up).
If you are going to buck the signs because your RV is not a commercial vehicle, and thus not a truck, you need local knowledge.
BTW, I know some "No Trucks" roads around Chicago where driving a pickup will get you a citation if the police are watching when you try to go through. No mercy for a RV, or even a school bus. There are alternate routes, you are expected to use them.
If it is Lakeshore Drive in Chicago "No Trucks" also means "No RVs." However, in 1961 we hauled our travel trailer down Lakeshore Drive from the north end of Chicago to the drawbridge, then followed Michigan Avenue out through the South Side. We didn't get caught, but I was navigator and my dad complained for the next three years about how I routed him through Chicago. Had I got him onto Lakeshore Drive in Evanston, we would have certainly been caught and ticketed.