Four-quadrant gate

A level crossing with manually-controlled full barriers at Chertsey, England. The barriers are rising.

A four-quadrant gate or full-barrier equipment is a type of boom barrier gate protecting a grade crossing. It has a gate mechanism on both sides of the tracks for both directions of automotive traffic. The exit gates blocking the road leading away from the tracks in this application are equipped with a delay, and begin their descent to their horizontal position several seconds after the entrance gates do, so as to avoid trapping highway vehicles on the crossing. In the UK, the exit-side barriers don't lower until the entrance-side barriers have lowered. Many people consider four-quadrant gates to be safer than two-quadrant gates because they prevent drivers from illegally driving their vehicles around lowered gates to try to beat a train. However, they are only safer if there is a way of ensuring that the crossing is clear before clearing the train driver's signals and allowing them to pass, as is always the case in the UK (explains why the barriers are lowered for long periods before the train arrives; the barriers are lowered with enough time that the train can be stopped if the crossing is obstructed).

In the UK, such crossings are categorised as manually-controlled barriers (MCB) because they are almost always manually-controlled, usually from a signal box or centre. Some are known as MCB-CCTV level crossings, because they are supervised by video link to the signal box from which they are remotely controlled. They can also be operated automatically, as long as the crossing is still checked for obstruction (i.e. obstacle detection technology). "Gates" and "Barriers" should not be confused: in American English, "gates" are used to describe level crossing barriers, as there are no longer traditional, opening gates. In British English, "barriers" refers to level crossing barriers, as some crossings still have actual gates. Therefore, saying "gates" to describe mechanised lifting barriers is incorrect.

The first four-quadrant gate in the United States was installed in 1952.^[1]^: 7 They have become common for new installations and replacements since. Unlike the UK, many are automated by the rail line's signal system. The first quad gate installation in the country with sensors to detect vehicles stopped in the tracks was installed in Groton, Connecticut in 1998.^[2] Eight of the eleven remaining grade crossings on the Northeast Corridor now have such setups.^[3]

References[]

^ Hellman, Adrian D.; Carroll, Anya A.; Chappell, Debra M. (March 2007). "Evaluation of the School Street Four-Quadrant Gate/In-Cab Signaling Grade Crossing System" (PDF). Federal Railroad Administration. Retrieved 1 February 2020.{{cite web}}: CS1 maint: url-status (link)
^ "Stuck crossing gate strands drivers on wrong side of the tracks". The Day. 4 November 1999. Retrieved 22 March 2015.
^ Dee, Jane E. (9 September 1999). "Amtrak To Put Up 7 Safer Gates". Hartford Courant. Retrieved 22 March 2015.

Four-quadrant gate

References[]

Further reading[]