The use of simulations of real-world settings can provide data relevant to ergonomics problems in a wide range of similar settings. This paper reports on a simulation of a freight service operation. It examines the effect of manipulating the type and format of information representation on the ability to update knowledge about the status of three vehicles. In addition, the effects of display type and the detection of violations of pre-learned rules on the ability to update are examined. The display format proved not to be a critical factor but the requirement to detect rule violations of a specific vehicle resulted in better memory-updating performance for that vehicle. The results are discussed in terms of a human memory mechanism, which is analogous to a computer operating system, involved in updating memory and detecting violations. Finally, the value of using this tool to examine complex cognitive processes relevant to the workplace is discussed.