(a) The Department of Administration may not pay an official or employee for per diem or transportation costs unless the travel is clearly necessary to benefit the state.

(b) The Department of Administration may not reimburse an official or employee or pay for more than the lowest tourist class fare for the most direct route unless

(1) tourist class accommodation is not available;

(2) waiting for tourist class accommodation would occasion a delay harmful to the state; or

(3) the Department of Administration finds that travel by tourist class accommodation is not in the best interest of the state, and authorizes other accommodation.

(c) When the Department of Administration authorizes more expensive travel under (b)(3) of this section, it shall file a justification for that authorization with the travel voucher. When fares other than tourist class are authorized under (b) of this section, the Department of Administration may not reimburse the official or employee or pay for more than the lowest first class fare available.

(d) Officials and employees are authorized to travel only the least number of days necessary to transact the business involved, to secure return passage, and to return.

(e) Every official and employee shall, unless otherwise authorized by law to travel outside the state, obtain prior approval for travel outside the state from the head of the official's or employee's department or from an immediate supervisor, or from the Department of Administration if the official or employee is not within a department or is not under the direct supervision of an official or supervisor. If an employee deviates materially from the travel authorized under this section, the employee must obtain approval for the deviation from the person who approved the travel before the Department of Administration may reimburse the employee for the travel.