§ 137. Transportation policy. It is hereby declared to be the policy of this state to regulate transportation by motor carriers in such manner as to recognize and preserve the inherent advantages of, and foster sound economic conditions in such transportation and among such carriers in the public interest; promote safe, adequate, economical and efficient service by motor carriers, and reasonable charges therefor, without unjust discriminations, undue preferences or advantages, and unfair or destructive competitive practices; improve the relations between, and coordinate transportation by and regulation of motor carriers and other carriers.