It is hereby declared to be the policy of the legislature to regulate motor carriers in the public interest to the end that the safety and welfare of the public in its use of the highways and of the transportation agencies by motor vehicle used thereon may be practiced; that the property of the state in its highways may be protected from unreasonable, improper and excessive use; that the inherent advantages of highway transportation may be recognized and preserved; that sound economic conditions in such transportation and among such carriers may be fostered; that the service by motor carriers may be adequate, economical, and efficient; that reasonable charges may be made therefor, without unjust discriminations, undue preferences or advantages, and unfair or destructive competitive practices; that relations between motor carriers and other carriers may be improved and coordinated; and that cooperation may be maintained with the governments of the United States and the several states, and with their duly authorized officials in carrying out the purposes and provisions of this chapter. This chapter shall apply to persons and motor vehicles engaged in interstate commerce to the extent permitted by the Constitution and laws of the United States and as provided herein.