The authority of the state highway department varies in the several states, but in general the departments serve in the dual capacity of general advisers to the county and township authorities on road matters and as the executive authority responsible for the construction of those highways that are built entirely or in part from state or federal funds. State highway departments consist of the commission or commissioner, and the technical and clerical staff required to perform the duties imposed on the state organization. To some extent the state highway departments are able to encourage economical and correct construction of highways by the township and county authorities by furnishing them standard plans and specifications and by formulating regulations to govern the character of construction, but such efforts are likely to be more or less ineffective unless the state authority has supervision of the allotment of state or federal funds to the various counties and townships. Nevertheless, most state highway departments do a great deal of advisory work in connection with the highway construction carried out by county and township authorities. State highway departments are supported by funds obtained in various ways, laws differing greatly in this respect. The necessary support is in some states appropriated from funds obtained by general taxation, and is in others obtained from automobile license fees. In still others, the funds are secured by a combination of the two methods mentioned above. In addition to these support funds, a certain part of the money obtained as federal aid may be employed for the engineering and inspection costs on federal aid roads. The above mentioned funds are required to maintain the state highway department. In addition, the departments have supervision of the expenditures of construction funds which can be used for road construction and maintenance, and may not be expended for salaries or other overhead expense. In a number of states, automobile license fees are set aside for financing road construction and maintenance, and the work paid for from the fees is carried out under the supervision of the state highway department. In a number of instances, state bonds have been issued for road construction, and the expenditure of the proceeds of the sale of road bonds has usually been supervised by the state highway department. All federal aid funds allotted to a state must be expended under the direction of the state highway department.