If a vehicle is over-dimensional (oversize) or overweight, a temporary permit is needed. This permit authorizes movement according to vehicle configurations and weight and contains routing information, travel regulations/restrictions, and safety requirements. Oversize or overweight load is any load carried by a vehicle that exceeds 8'-6" in width, 80'-0" in length or 14' in height. Examples of an oversize load include modular buildings and construction equipment.
For more information on the restrictions you can locate them at the Caltrans website.