When turning left at an intersection and you have to wait for a gap in the oncoming traffic, stop so the front tires of the vehicle are on the front crosswalk line. This technique allows you to be commited to the left turn, but not be in the intersection in the event something goes awry.
First and foremost, this driving technique is an absolute requirement for a road test regardless of the vehicle type or configuration.
Questions arise about how heavy is a truck, RV trailer, or truck-trailer combination. If your truck-trailer, or RV unit exceeds specified gross vehicle weights, the driver will require a higher class of licence. In British Columbia, for example, if you are towing a trailer exceeding 4,600kg (10,100lbs), but neither the truck nor trailer has air brakes, the driver is required to have a heavy trailer endorsement (Code 20).
The best way to find out is to put it on a scale.