Lines vs. no lines: do lines connecting related information improve performance on ambulance dispatch tasks?

Display design can play a vital role in the performance of operators controlling complex systems. This paper presents a follow-up study to an earlier one which found that when completing an ambulance dispatch task, participants using a display that had good task-to-display compatibility performed better on more complex dispatch tasks than participants using a display that had poor task-to-display compatibility [1], In the earlier study, the information on the ambulance status display was reorganised so that it mirrored the relative geographical positions of the ambulance stations. Lines were included to show how each station was related to neighboring stations. It was not clear from this study whether the performance improvements were due to the re-organisation or the lines. The purpose of our study is to determine whether it was the connecting lines or the semantically compatible display organisation that was responsible for the performance improvements. Thirteen students who were novices to ambulance dispatch participated in an experiment where they were asked to complete simulated ambulance dispatch tasks with various levels of difficulty. The results showed no significant difference in dispatch performance between the display with connecting lines compared to the display that did not have connecting lines. This result is similar to findings from [2] who also found no benefits from connecting lines. We conclude that the semantic organisation of the display is more likely to be responsible for the performance improvements.