Nos. 10570, 10617. Argued November 4, 1966. Decided February 6, 1967. J.W. Alexander, Jr., Charlotte, N.C. (Ernest W. Machen, Jr., and Blakeney, Alexander Machen, Charlotte, N.C., on brief), for petitioner Overnite Transp. Co. Hugh J. Beins, Washington, D.C., (Michael F. Grdina, Willoughby, Ohio, on brief), for petitioner Teamsters Local Union No. 171. Gary Green, Atty., N.L.R.B. (Arnold Ordman, Gen. Counsel, Dominick L. Manoli, Associate Gen. Counsel, Marcel Mallet-Prevost, Asst. Gen. Counsel, and