(a) In a county with a population of 372,000 to 400,000, a sheriff, deputy, constable, or other peace officer of the county or a municipality located in the county may not be required to be on duty more than 48 hours a week unless the peace officer is called on by a superior officer to serve during an emergency as determined by the superior officer.
(b) Hours of duty over 48 hours a week, compiled by a peace officer under Subsection (a), may be treated as overtime and may be deducted from future required hours of duty if:
(1) the overtime is used within one year after it is compiled; and
(2) the peace officer obtains the permission of the superior officer.