Taxes prescribed by this chapter are declared to be compensatory for the use of the public roads of this state by operators of motor vehicles taxed under the provisions of this chapter and are further declared to be a fair contribution to the cost of constructing and maintaining the public roads of this state. The administration and enforcement of this chapter and all regulations and restrictions imposed hereby and authorized to be imposed by this chapter are declared to be for the purpose of conservation of the property of the state and in the interest of safety in the use of its roads.