Tennessee Code Title 4. State Government § 4-3-2302

(a) The administrator and head of the department shall be the commissioner of transportation, who shall be a person qualified by training and experience to perform the duties of the commissioner's office.

(b) The commissioner shall be appointed by the governor.

(c) The commissioner shall serve at the pleasure of the governor and shall receive a salary in accordance with § 8-23-101.

(d) In the event of death, resignation, temporary incapacity or removal of the commissioner, and prior to the appointment of the commissioner's successor, the governor may appoint a qualified employee of the department of transportation to serve as acting commissioner. The commissioner may appoint, during the commissioner's absence from the state, a qualified employee of the department to serve as acting commissioner for the duration of the absence. In either case, the acting commissioner shall have all the duties, functions and powers of the commissioner during the commissioner's absence or incapacity, or until the commissioner's successor is duly qualified and appointed.