Abstract
Driver information systems based on variable message sign (VMS) technology can potentially make a significant contribution to reducing network stress. However, to realise these benefits it is necessary to pay particular attention to a number of key issues. The paper outlines the principles on which successful development is based and discusses some of the more important issues involved in operational strategy development, the system engineering design, the management and operation of the system as well as the establishment of the learning process through a set of comprehensive evaluation procedures. (A)