The RTA published its Guide to Traffic Generating Developments in the mid-1990s. As part of the studies supporting this, document, a number of shopping centres were the subject of detailed trip generation and parking studies in 1978 and again in 1990. Since then there have been some recent changes to the type and operation of shopping centres and also ongoing societal and economic changes which collectively have the potential to impact on the relevance and reliability of the information in the Guide to Traffic Generating Developments. These include: Changes to retail trading hours in particular Sunday.