Over-sized loads are large items or bulk items that cannot be separated into smaller parts. It's a giant singular item instead of large group of items. If an item can be rearranged and removed they cannot be considered an over-sized load. Knowing this ahead of time will save you the trouble of applying for a permit in your state and being turned down.
Height limits for getting approved for an over-sized permit differ for transporting an over-sized load but the most common limit is 13 feet and six inches. Height requirements are sometimes different between states due to height clearances that would allow an over-sized load to pass, such as certain bridges or tunnels. A special transportation permit including a route that will avoid low bridges will then be needed if the load exceeds these measurements.
The width of an over-sized load needs to be a minimum of eight feet and six inches, although state laws can vary with this requirement. Take this into account if a load is 8 feet, 5 inches and the driver will have difficulty maneuvering on most highways. In some states certain highways and tunnels will not allow over-sized loads based on their width. A special transportation permit will then be needed if the load exceeds these measurements.
If the over-sized load impedes the driver's vision or takes up more than one lane, there must be a tailing car and a pilot vehicle behind and in front of the truck with the load to alert other drivers to the over-sized load. The truck usually has at least one flashing light or both of its flashers on while on the road, as well. When driving at night, flashing lights are required. Sometimes the tailing vehicle and pilot also have these lights on to let other vehicles on the road know this truck is going slow and might take up two lanes. In many states, over-sized loads are not allowed on the road at night.
Before you drive an over-sized load over your state's borders, you will need to obtain a license for each state through which you will be transporting your load. To obtain these licenses you will need to contact each state's department of transportation. Exceeding each state's basic requirements for an over-sized load may require special state permits and possibly police escorts.
