In some areas, such as California, highway medians are sometimes no more than a demarcated section of the paved roadway, indicated by a space between two sets of double yellow lines. Such a double-double yellow line or painted median is legally similar to an island median: vehicles are not permitted to cross it, unlike a single set of double yellow lines which may in some cases permit turns across the line.[4] This arrangement has been used to reduce costs, including narrower medians than are feasible with a planted strip, but research indicates that such narrow medians may have minimal safety benefit compared to no median at all.[5]