Tex. Ins. Code art. 5.77

The Board of Insurance Commissioners is hereby authorized and empowered to make or approve and promulgate premium rating plans designed to encourage the prevention of accidents, to recognize the peculiar hazards of individual risks and to give due consideration to interstate as well as intrastate experience of such risks for Workmen's Compensation, Motor Vehicle and other lines of Casualty Insurance to be applicable separately for each class of insurance, or in combination of two or more of such classes. Such plans may be approved on an optional basis to apply prospectively, or retrospectively and may include premium discount plans, retrospective rating plans or other systems, plans or formulas, however named, if the rates thereby provided are not excessive, inadequate or unfairly discriminatory. The Board shall also have authority to make or approve and promulgate such reasonable rules and regulations as may be necessary, not in conflict with provisions of this Act.