This primitive clearance car of the Rio Grande consists of a simple wooden outline. The Denver and Rio Grande Railroad, generally referred to as the Rio Grande, became the Denver and Rio Grande Western Railroad in 1920 and is today a Fallen

A clearance car is a type of railroad car in maintenance of way service. A railroad car or railway carriage is a Vehicle on a rail transport system (railroad or railway that is used for the carrying of Cargo or MOW redirects here For other meanings see MOW (disambiguation. Its purpose is to check the clearances around the tracks and ensure that trains conforming to the railroad's standard loading gauge or dynamic envelope will not encounter any obstruction. A loading gauge is the envelope or contoured shape within which all Railroad cars, Locomotives coaches Buses Trucks and other 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.

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.

More recently, clearance cars using lasers for measurement have come into service. These are generally HiRail trucks—road vehicles with supplemental rail wheels. A Road-rail vehicle is a Self-propelled Vehicle that can be legally used on both Roads and rails.

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.

See also

• Wayobjects

External links

• MOW equipment page 11 at North East Rails, including several clearance cars. 0-9 Note for 4-4-0 2-6-4T 0-4-4-0 etc See Whyte notation or UIC classification A B
• Article on the Pennsylvania Railroad clearance car at the Pennsylvania Railroad Technical and Historical Society's site, written by a former clearance car crewmember.