VISIBILITY OF TEXT AND ICON HIGHWAY SIGNS UNDER DYNAMIC VIEWING CONDITIONS

Threshold sizes for accurate identification were determined for three different types of highway signs (text, icon, and modified icon) under two conditions of horizontal target motion (60 degrees and 120 degree s per second). The two iconic versions were superior to the text versi on in nearly all cases, and this benefit of the pictorial format was e ven more pronounced in the higher-velocity condition. The advantage of the modified icon signs over the standard icon signs that had been de termined in previous work was replicated here under the low-velocity c ondition but essentially disappeared under the higher-velocity conditi on. Sign-reading performance was found to be related to dynamic visual acuity (with Landolt-C targets) under the two velocity conditions. Re sults are discussed in terms of the ''low-pass format'' for sign desig n suggested by previous researchers and in terms of the potential util ity of dynamic acuity for the driving setting.