Background This book is the most obvious outcome of the “COST 351, WATMOVE” project (see www. watmove. org). For most readers these terms probably mean little so some explanation is called for. In 2001/2002 a small group led by Kent Gustafson of the Swedish Road and Traf c Institute (VTI) made a proposal to the European programme on “Co-operation in Science and Technology” (COST). They proposed that a pan-European team be set up to study the issue of “Water Movements in Road Pavements and Embankments” (acronym = WATMOVE). The COST organisation agreed the proposal and the study formally began in December 2003 with the s- port of COST. Due to ill-health, Kent was not able to lead the project and I was asked by the Management Committee to chair the project team. Scope of the Book This book is NOT about “Water and Roads”, nor on “Water on Roads”. There are other books which deal with surface water drainage in great detail and there are other source materials that deal with the impact of roads on water in the general environment. To cover every aspect of the interaction between water and highways would have required a much greater effort and a much thicker book. So this book seeks to limit itself to: (i) Water inside the road construction and the underlying subgrade soils and rocks; 1 (ii) Water from the surface down to the phreatic surface, and (iii) Water in the road and ground between the fence-lines of the highway.