49 CFR §391.33

1. (a)In place of, and as equivalent to, the road test required by § 391.31, a person who seeks to drive a commercial motor vehicle may present, and a motor carrier may accept—
   1. (1)A valid Commercial Driver's License as defined in § 383.5 of this subchapter, but not including double/triple trailer or tank vehicle endorsements, which has been issued to him/her to operate specific categories of commercial motor vehicles and which, under the laws of that State, licenses him/her after successful completion of a road test in a commercial motor vehicle of the type the motor carrier intends to assign to him/her; or
   2. (2)A copy of a valid certificate of driver's road test issued to him/her pursuant to § 391.31 within the preceding 3 years.
2. (b)If a driver presents, and a motor carrier accepts, a license or certificate as equivalent to the road test, the motor carrier shall retain a legible copy of the license or certificate in its files as part of the driver's qualification file.
3. (c)A motor carrier may require any person who presents a license or certificate as equivalent to the road test to take a road test or any other test of his/her driving skill as a condition to his/her employment as a driver.