1. Professor, School of Highway Engineering, Changsha Univ. of Science & Technology, Chiling Rd. No. 45, Changsha, Hunan, 410076, P.R. China; presently, Pavement Engineering Supervisor, Texas Dept. of Transportation, 4203 Bull Creek Rd., No. 39, Austin, TX 78731. E-mail: dchen@dot.state.tx.us