Any motor vehicle may be operated under the conditions specified in Section 66-3- 802 NMSA 1978 when equipped with the two lighted lamps upon the front thereof capable of revealing persons and objects seventy-five feet ahead in lieu of lamps required in Section 66-3-830 N.M. Stat. Ann. or Section 66-3-832 N.M. Stat. Ann.; provided, however, that at no time shall it be operated at a speed in excess of twenty miles an hour.