1. Ishikawa National College of Technology, Tsubata, Ishikawa, 929-03 Japan
2. Pavement Section, Research Institute of Japan Highway Public Corporation, 1-4-1 Tadao, Machida, Tokyo, 194 Japan
3. Department of Agricultural Engineering, Tokyo University of Agriculture, 1-1-1 Sakuragaoka, Setagaya-ku, Tokyo, 156 Japan