[1] ZAG Ljubljana, Geotech & Traff Infrastruct Dept, Ljubljana, Slovenia
[2] Univ Nottingham, Nottingham NG7 2RD, England
[3] Norwegian Univ Sci & Technol, N-7034 Trondheim, Norway
[4] VTT Tech Res Ctr Finland, Helsinki, Finland
[5] Univ Helsinki, FIN-00014 Helsinki, Finland
[6] ETH, Zurich, Switzerland