A box junction is a roadtraffic control measure designed to prevent congestion and gridlock at junctions. 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.
Box junctions were introduced in the UK during 1967, following a successful trial in London.[1] In both Ireland and the United Kingdom (where cars drive on the left), drivers may enter the box and wait when they want to turn right and are stopped from doing so only by oncoming traffic or by other vehicles waiting to turn right.[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.
^"13.6: 'Do Not Block Intersection' lines", Highway Safety Design Standards, Part 2: Road Signs and Pavement Markings Manual, Philippines: Department of Public Works and Highways, p.127