Past investigations and experimental studies dealing with the visual detection of either nonreflectorized or reflectorized objects or targets in the driving environment at night have been limited primarily to foveal or line-of-sight visual detection. A geometric modelis developed to analyze reflectorized targets located ahead of a car at different locations along a tangent-curve and curve-tangent section of a highway. Typical night driving eye scanning data are also presented. The model demonstrates that in many cases unknown or unexpected reflectorized targets, such as a reflectorized license plate or an advance warning sign, will appear initially at moderately large peripheral angles up to 15 deg or more away from a driver's fovealeye fixation point, or line of sight. A field study involving the foveal and peripheral detection of a reflectorized target is presented to show that peripheral visual detection distances decrease considerably as the peripheral visual angle away from the fovea, or line of sight, increases. A 10 deg peripheral visual detection angle results in an average visual detection distance approximately one-half ofthe average foveal detection distance. It is concluded that in a situation where drivers approach or negotiate a curve at night, where reflectorized objects or targets will become visible for the first time probably inthe periphery of a driver's visual field, and where there is a need for early detection, the reflectivity of the target should be increased to ensure timely recognition, information processing, and decision making, and appropriate control actions. This paper appears in transportation research record no. 1213, Human performance and highway visibility: design, safety, and methods.
Abstract