1. Swedish Transport Administration , Gibraltargatan 7 , Malmö , Sweden .
2. Department of Building and Environmental Technology , Faculty of Engineering, Lund University , Box 118 , Lund , Sweden .
3. École polytechnique de Bruxelles, Université Libre de Bruxelles , Laboratory of Image Synthesis and Analysis, Campus de Solbosch, ULB – LISA CP165/57 , Avenue Franklin D. Roosevelt 50 , Brussels , Belgium .