| Previous research found that the airplane silhouette denoting a nearby airport contains sufficient implied directional information to cause some degree of confusion when displayed in directional opposition to an associated traffic guidance arrow. These findings were expanded by testing other traffic symbols. While it was confirmed that some additional symbols appear to be confusing, another surprisingly turned out not to be so. Specifically, a logo that contained a directional arrow in its design was not found to be confusing. One reason suggested for this, and subsequently explored in this research, is that the logo's arrow was too small to be effectively disruptive. Building on this suggestion, the current research varied the size of a traffic directional arrow relative to the size of its associated airplane silhouette and measured subject response latencies and errors for a simple forced choice (left, right) task. It was determined that as the relative size of the directional arrow increases, average latencies and error rates decrease, but only to the point of the arrow being 80--90% the size of the silhouette. After this point, no substantial further performance improvements were found. Based on these results, a more optimal traffic guidance sign design was tested, with the results demonstrating marked subject performance improvements. However, unlike the previous studies, errors tended to occur when subjects responded very quickly suggesting that they overly anticipated what the next stimulus would be, thereby reacting to their anticipated thoughts rather than first thinking through what was displayed to them. Nonetheless, this scenario is unlikely to occur in practice. Thus, this research's implications are twofold. First, traffic guidance arrows should be made larger in practice, to about 90% of their associated traffic symbol's size. Second, the techniques used herein could be reapplied as a means to determine the relative degree of informational content a given symbol contains, thereby leading to the development of visual display designs that optimize human performance. |
