Is there a maximum width for vehicles traveling on the highway?

The normal legal width is 8 ft 6 in.  Some of the exceptions that allow a width over 8 ft 6 in include:

• Implements of husbandry (a.k.a. farm vehicles) on interstate roads between sunrise and sunset.
• Implements of husbandry on non-interstate roads at any time of day (with required lighting in working order).
• Commercial vehicles with a permit. 

Review North Dakota Century Code: 39-12-04.