In Montana, there are special rules regarding trucking and transferring loads around the state. For over-sized trucks, an oversize permit must be requested and received. This permit is acceptable for three to five days before it expires, giving drivers enough time to pass through the state.
There are other restrictions drivers may face when driving a large vehicle through the state. Loads that are smaller than 10 feet by 14.5 feet by 110 feet long can travel at all hours day or night, but those with larger vehicles may have extra restrictions. For instance, Red Route Highway travel is not allowed after 3:00 p.m. from Friday through Saturday morning at sunrise for those with vehicles exceeding the above measurements. Holiday travel is also restricted for vehicles above that size, although those under that length, width and height are typically able to be on the roads at any time.
As someone driving on the highway with these vehicles, it's important that the drivers know these restrictions. The restrictions make sure heavy and over-sized vehicles aren't on the road during high-traffic times, so there are fewer chances for accidents. If someone is involved in an accident with vehicles of this size, the outcome can be devastating.
Many times, escorts are provided to vehicles that exceed typical sizes. For example, if a vehicle is wider than 16.5 feet, one escort is required on interstate highways. For those over 120 feet long, an escort is required as well. On two-lane highways, any vehicle over 12.5 feet requires one escort, while those over 16.5 feet require two. These escorts are there to make sure traffic is clear and aware of the incoming over-sized vehicle.
Source: Heavy Haul Trucking, "Montana Oversize Permits" accessed Feb. 02, 2015