Michigan Compiled Laws, Chapter 254. Bridges § 254.231

Sec. 11. The exercise of the powers granted by this act will be in all respects for the benefit of the people of the state, for the increase of their commerce and prosperity, and for the improvement of their health and living conditions, and as the operation and maintenance of the project authorized by this act will constitute the performance of essential governmental functions, the authority shall not be required to pay any taxes or assessments upon the project or any property acquired or used by the authority under the provisions of this act or upon the income therefrom, and any bonds issued under the provisions of this act, their transfer and the income therefrom (including any profit made on the sale thereof) shall at all times be free from taxation within the state.