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A clearance car is a type of
File:Structure Gauging Train at York station.jpg, Structure gauging train at
MOW equipment page 11
at North East Rails, including several clearance cars.
at the
A clearance car is a type of railroad car
A railroad car, railcar (American and Canadian English), railway wagon, railway carriage, railway truck, railwagon, railcarriage or railtruck (British English and UIC), also called a train car, train wagon, train carriage or train truck, is a ...
in maintenance of way
Maintenance of way (commonly abbreviated to MOW) refers to the maintenance, construction, and improvement of rail infrastructure, including tracks, ballast, grade, and lineside infrastructure such as signals and signs.
Track
The most fundamen ...
service. Its purpose is to check the clearances around the tracks and ensure that trains conforming to the railroad's standard loading gauge
A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
or ''dynamic envelope
A loading gauge is a diagram or physical structure that defines the maximum height and width dimensions in railway vehicles and their loads. Their purpose is to ensure that rail vehicles can pass safely through tunnels and under bridges, and ke ...
'' will not encounter any obstruction. Additionally, by measuring the actual clearances along a route, the railroad can determine whether outsize loads can be accommodated along that route, and the largest size feasible.
Design
Early clearance cars simply consisted of an outline of the system loading gauge attached to a railroad car, which would be towed along the route to ensure the clearances were still sufficient. Later clearance cars functioned by using physical feelers—rods which extended from the car in all directions which would be deflected back by obstructions. These would be connected to instrumentation which displayed the actual clearance at that point. These feelers have an advantage in that they bounce back and do not break if they do hit something. Subsequently, clearance cars usinglaser
A laser is a device that emits light through a process of optical amplification based on the stimulated emission of electromagnetic radiation. The word "laser" is an acronym for "light amplification by stimulated emission of radiation". The ...
s for measurement have come into service. These are generally HiRail trucks – road vehicles with supplemental rail wheels.
Benefits
The clearance car allowed accurate and speedy measurement of the clearances for a structure. Generally they were only owned by larger railroads; other railroads sometimes leased them for short periods. Some were self-propelled, while others were locomotive-hauled.Gallery
York Station
York railway station is on the East Coast Main Line serving the city of York, North Yorkshire, England. It is north of and on the main line it is situated between to the south and to the north. , the station is operated by London North East ...
File:TSHR Structure Gauge Test Car 02.jpg, Taiwan High Speed Rail clearance car
File:Railroad clearance car.jpg, Railroad clearance car front view
See also
* Clearance space *Structure gauge
A structure gauge, also called the minimum clearance outline, is a diagram or physical structure that sets limits to the extent that bridges, tunnels and other infrastructure can encroach on rail vehicles. It specifies the height and width of pl ...
* Wayobjects
Rail terminology is a form of technical terminology. The difference between the American term ''railroad'' and the international term ''railway'' (used by the International Union of Railways and English-speaking countries outside the United Sta ...
References
External links
MOW equipment page 11
at North East Rails, including several clearance cars.
at the
Pennsylvania Railroad Technical and Historical Society The Pennsylvania Railroad Technical and Historical Society (PRRTHS) is a railroad historical society founded in 1974 and organized as a Pennsylvania non-profit corporation and recognized as a 501(c)(3) tax-exempt organization by the United States In ...
's site, written by a former clearance car crewmember.
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Maintenance of way equipment