Engineering of traffic markers to satisfy requirements of perceptual space.

Many laboratory studies show that a two dimensional object having a flat surface cannot communicate its spatial plane accurately. This fact is applied to driving situation since a traffic marker is to be obeyed only when it face the driver directly. Laboratory studies are reviewed, showing that the conventional flat marker leads to confusions of reference consistent with theoretical expectations. Other laboratory work reviewed shows that a curved marker will reduce error greatly. Practical implications are discussed.