1. Chf. Expert Statistical Applications, Mat. and Res. Div., Israel Public Works Dept., 55 Ben-Zvi Rd., Tel Aviv 61940, Israel.
2. Assoc. Prof. of Civ. Engrg., Technion—Israel Inst. of Technol., Transp. Res. Inst., Technion City, Haifa 32000, Israel.
3. The Harry Oppenheimer Prof. of Engrg., Technion—Israel Inst. of Technol., Transp. Res. Inst., Technion City, Haifa 32000, Israel.