1. Assoc. Prof., Ctr. for Transp. Res., Dept. of Civ. Engrg., Nat. Univ. of Singapore, 10 Kent Ridge Crescent, Singapore 0511.
2. Res. Asst., Ctr. for Transp. Res., Dept. of Civ. Engrg., Nat. Univ. of Singapore, 10 Kent Ridge Crescent, Singapore 0511.
3. Sr. Lect., Ctr. for Transp. Res., Dept. of Civ. Engrg., Nat. Univ. of Singapore, 10 Kent Ridge Crescent, Singapore 0511.