Box junction
Encyclopedia : B : BO : BOX : 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 rather only two lines crossing each other in the box junction, as it is used widely in Singapore) 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, drivers may enter the box and wait when they want to turn right, and are only stopped from doing so by oncoming traffic, or by other vehicles waiting to turn right. [link]
Similar yellow boxes may be painted on other areas of roadway (such as the exits from emergency vehicle depots) which must be kept free of queuing traffic.
Box junctions are currently used in the United Kingdom (where they were invented), New York City, some parts of Colorado, Hong Kong, Singapore, Malaysia (particularly Kuala Lumpur), the Republic of Ireland, Malta, South Africa, Taiwan, major cities in Brazil and Canada.
Boxes are also used in Perth, Western Australia at rail crossings and some intersections.
Alternatives to the box junction
In the U.S. state of California, the Anti-Gridlock Act of 1987 bans gridlocking at all intersections, rail crossings, and marked crosswalks. Drivers cannot enter any of the three until they are certain their vehicle can clear it.See California Vehicle Code Section 22526.[link] No special road markings are used to indicate this rule. However, the Act allows local governments to post "DO NOT BLOCK INTERSECTION" signs at their discretion, and many do.
References
| Types of road junction | |
| Interchanges (grade separated) | Cloverleaf - Diamond - Directional T - Diverging diamond Parclo - Trumpet - SPUI - Stack |
| Intersections (at-grade) | Box junction - Continuous flow - Crossroads - Hook turn Jughandle - Michigan left - Roundabout - 3-way junction - Traffic circle |
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