- Box junction
A box junction is a traffic control measure designed to prevent gridlock at busy road junctions. The surface of the junction is marked with a criss-cross grid of diagonal painted lines (or only two lines crossing each other in the box junction), and vehicles may not enter the area so marked unless their exit from the junction is clear (or, if turning, to await a gap in the oncoming traffic flow). In the United Kingdom and Republic of Ireland (where, in both places, 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.
Similar yellow boxes may be painted on other areas of roadway which must be kept free of queuing traffic such as the exits from emergency vehicle depots or level crossings.
Box junctions are currently used in the United Kingdom, New York City and its Tri-State region, some parts of Colorado, Cyprus, Hong Kong, Singapore, Malaysia, the Republic of Ireland, Serbia, Malta, Portugal, South Africa, Taiwan, major cities in Brazil, Canada & Trinidad & Tobago.
In Australia, New Zealand and EU (excluding the United Kingdom and Ireland), the road rules state that every intersection is a box: that is, you may not enter any intersection unless there is clear space on the other side, whether it is marked or not. In the European Union this also applies to junctions with a minor road within the waiting area of a stoplight on the major road. This is generally respected, but the diagonal grid is still painted on some congested intersections to remind drivers of the rule and on rail crossings where blocking the intersection could cause a serious accident.
In many U.S. states, laws intending to decrease gridlocking at intersections, rail crossings, and marked crosswalks have been enacted which prohibit motorists from entering any of the three until they are certain their vehicle can clear it. No special road markings are used to indicate this rule, but some governments post "DO NOT BLOCK INTERSECTION" signs to increase awareness of the law at problematic intersections.
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