With growing populations and important economic activity, the pressure imposed upon a territory by construction projects is considerable. This is particularly the case in Canton Vaud (the French speaking part of Switzerland). Large urban centres endure significant changes to their structure, as do historic buildings. The surface area of towns and cities is also on the increase. Indeed causing them to be gradually integrated into the urban network. The scale of housing construction and infrastructure expansion does not spare medium sized towns, which also undergo major upheavals. Known archaeological urban remains, and those as yet undiscovered, are therefore seriously threatened. Issues of detection, conservation and study of archaeological remains are intrinsically linked to planning and development. The archaeological services dedicated to heritage protection have to ensure the safeguarding of archaeological remains and in-situ conservation and if this proves impossible, scientific documentation through archaeological excavation. The aim of this presentation is to illustrate the tools used by the Canton Vaud to protect archaeological remains in advance (perimeters of protection, prior studies of fortification location and legislative measures), to show the types of recurring operations seen in the last few years (such as the repair of public infrastructures and the transformation of old buildings) and the results these operations have contributed in scientific terms as well as their scope in providing the general public with knowledge of their town or neighbourhood. Finally there is also the question of practical limitations in cases when it is impossible to conserve remains in-situ and their destruction is thus conceded.