Dr Roger Lewis is a Senior Lecturer in the Department of Mechanical Engineering, University of Sheffield, where his main research interests include railway and automotive tribology, and design of tools to solve wear and failure problems in industry. Professor Ulf Olofsson is Head of the Department of Machine Design and research leader of the tribology group in the Royal Institute of Technology, Sweden. His main research interests include interfaces and especially simulation and prediction of friction and wear, mainly applied to problems in railways and mechanical engineering.