1. Civil Engineer, JK Williams Contracting Pty Ltd., Penrith, NSW, Australia; formerly, Honours Student in Civil Engineering Program, School of Civil Engineering, Univ. of Western Sydney, Penrith, NSW 2057, Australia.
2. Senior Lecturer in Civil Engineering, School of Civil Engineering, Western Sydney Univ., Penrith, NSW 2057, Australia.
3. Senior Lecturer in Railway and Civil Engineering, Birmingham Centre for Railway Research and Education, School of Engineering, Univ. of Birmingham, Birmingham B15 2TT, U.K.; formerly, Technical Specialist, RailCorp, Sydney, NSW 2000, Australia; Visiting Executive Fellow, Dept. of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139-4307 (corresponding author).