Texas Government Code - GOV'T § 660.044. Use of Single Motor Vehicle by Multiple Employees

(a) If two, three, or four state employees who are employed by the same state agency travel on the same dates with the same itinerary to conduct the same official state business, only one of the employees may be reimbursed for mileage.

(b) If more than four state employees who are employed by the same state agency travel on the same dates with the same itinerary to conduct the same official state business, a state agency may reimburse for mileage only on the basis of one motor vehicle for each four employees and for any fraction in excess of a multiple of four employees.

(c) Subsections (a) and (b) do not apply to a group of state employees if the chief administrative officer of the state agency that employs the employees determines before travel that it is not feasible for the employees to travel together in the same motor vehicle.  This determination may be made only for reasons related to official state business.