This publication, now in its second edition (2010), has been completely revised and updated since first published in 2002. It relates to human-computer interface (HCI) systems provided for people operating industrial processes and activities on facilities such as chemical plant, power stations and oil refineries. HCI systems are one of a number of key areas that can influence - and optimise - human performance in the area of a centralised control room, so important in maintaining process and major hazard safety. EEMUA 201 gives guidance on: the factors to take into account when designing an HCI; display hierarchies; screen display format design; and control room design attributes which affect HCIs. It is for use by engineers and managers in both user and contracting organisations. The objective is not only to make plants more operable, efficient and able to avoid abnormal situations, but to be able to better manage such situations should they occur.