The surface of the junction is typically marked with a yellow criss-cross grid of diagonal painted lines (or only two lines crossing each other in the box), and vehicles may not enter the area so marked unless their exit from the junction is clear, or they are intending to turn and are prevented from doing so by oncoming traffic, or other vehicles on the box waiting to turn.
[2] Box junctions may be painted on other areas of roadway which must be kept free of queuing traffic, such as exits from emergency vehicle depots, level crossings and car parks.
Box junctions are most widely used in many European countries such as Cyprus, Finland,[3][4] Ireland, Malta, Portugal, Serbia and the United Kingdom; in parts of the United States, such as New York and Colorado;[5] and other countries, including Canada, [citation needed] Hong Kong,[6] Singapore, Indonesia,[7] Malaysia,[8] the Philippines,[9] South Africa,[10] Taiwan,[11] India[12] and Brazil.
[13] Several U.S. states have enacted laws intending to decrease gridlock at intersections, railroad crossings, and marked crosswalks which prohibit motorists from entering any of the three until they are certain their vehicle can clear it, as recommended by Uniform Vehicle Code section 11–1112.
[18] No special road markings are used to indicate this rule, but some governments post warning signs to increase awareness of the law at problematic intersections.