Mich. Comp. Laws § 254.151

Sec. 1. Issuance of revenue bonds for public works. The state bridge commission hereinafter created is hereby authorized and empowered to acquire by purchase and to construct, or partly acquire and partly construct, and to improve, enlarge, reconstruct, own, equip, operate and maintain the public works hereinafter specified, and to issue revenue bonds, payable solely from earnings, to pay the cost of such works.