34 Tex. Admin. Code § 1.100
In each fiscal year, a municipality or county that engages in enforcement under Transportation Code, Chapter 644 (Commercial Motor Vehicle Safety Standards) may retain fines collected from such enforcement in an amount not to exceed 110% of the municipality or county's actual expenses for enforcement of that chapter in the preceding fiscal year, as determined by the comptroller after reviewing the most recent municipal audit conducted under Local Government Code, § 103.001 (Annual Audit; Financial Statement) or the most recent county audit conducted under Local Government Code, Chapter 115 (Audit of County Finances). If the most recent audit does not reflect actual expenses incurred by the municipality or county for the enforcement of Chapter 644, the municipality or county may retain fines in an amount not to exceed 110% of the amount the comptroller estimates would be the municipality or county's actual enforcement expenses during the year.
34 Tex. Admin. Code § 1.100