1. Division of Highway Engineering, Royal Institute of Technology, Brinellvägen 34, 100 44 Stockholm, Sweden.
2. AVECO bv, Eisenhowerlaan 6, P.O. Box 8270, 3503 RG Utrecht, The Netherlands.
3. Division of Road and Railroad Engineering, Delft University of Technology, P.O. Box 5048, 2600 GA Delft, The Netherlands.