Pennsylvania Railroad 0-4-0 No. 713, a Class A5, travels down the street in Atlantic City, NJ on April 25, 1954.

47 locomotives of this type were built by the PRR's Juniata Shops. Photo by Douglas Wornom.

(Audio-Visual Designs, Earlton, NY, Public domain, via the W. Lenheim Collection)



Under the Whyte notation for the classification of steam locomotives, 0-4-0 represents one of the simplest possible types, that with two axles and four coupled wheels, all of which are driven. The wheels on the earliest four-coupled locomotives were connected by a single gear wheel, but from 1825 the wheels were usually connected with coupling rods to form a single driven set.

The notation 0-4-0T indicates a tank locomotive of this wheel arrangement on which its water and fuel is carried on board the engine itself, rather than in an attached tender.

In Britain, the Whyte notation of wheel arrangement was also often used for the classification of electric and diesel-electric locomotives with side-rod-coupled driving wheels.

Under the UIC classification used in Europe and, in more recent years, in simplified form in the United States, a 0-4-0 is classified as B (German and Italian) if the axles are connected by side rods or gearing and 020 (French), independent of axle motoring. The UIC's Bo classification for electric and diesel-electric locomotives indicates that the axles are independently motored, which would be 0-2-2-0 under the Whyte notation.


Schematic of 0-4-0 steam locomotive wheel arrangement, front of locomotive on left.

(Gwernol, Public domain, via Wikimedia Commons.)



0-4-0 locomotives were built as tank locomotives as well as tender locomotives. The former were more common in Europe and the latter in the United States, except in the tightest of situations such as that of a shop switcher locomotive, where overall length was a concern. The earliest 0-4-0 locomotives were tender engines and appeared as early as c. 1802. The 0-4-0 tank engines were introduced in the early 1850s. The type was found to be so useful in many locations that they continued to be built for more than a century and existed until the end of the steam era.

A four-wheeled configuration, where all the wheels are driving wheels, uses all the locomotive's mass for traction but is inherently unstable at speed. The type was therefore mainly used for switcher locomotives.


Baltimore and Ohio Railroad 0-4-0 Atlantic No. 2 1832, the Grasshopper at the B&O Railroad Museum.

(James G. Howes, Attribution, via Wikimedia Commons)


Tank locomotives

An early example of the 0-4-0 vertical boiler type was the Baltimore and Ohio Railroad's Atlantic No. 2, built in 1832 by Phineas Davis and Israel Gartner. In the United States, the 0-4-0 tank locomotive was principally used for industrial railway purposes.


0-4-0 United States-built tender locomotive for Switching Service. Built for the Tinplate Company of India, Ltd. by the Vulcan Iron Works.

(Locomotive Cyclopedia of American Practice, Public domain, via Wikimedia Commons)


Tender locomotives

In the United States, the Best Friend of Charleston was the first locomotive to be built entirely within the United States. It was built in 1830 for the South Carolina Canal and Rail Road Company by the West Point Foundry of New York.

The John Bull was built by Robert Stephenson and Company for the Camden and Amboy Railroad in New Jersey in 1831, but was later rebuilt as a 2-4-0.

The Pennsylvania Railroad kept producing 0-4-0 classes long after all other major railroads had abandoned development of the type, building their final A5s class into the 1920s. The A5s was a monster among 0-4-0s, larger than many 0-6-0 designs, with modern features found on few others of its type, such as superheating, power reverse, and piston valves. The Pennsy continued to build the type because it had a large amount of confined and tight industrial track, more than most other railroads had.


An EMD Model 40 at the Travel Town Museum in Los Angeles, California.

(Klaus Nahr from Germany, CC BY-SA 2.0 <>, via Wikimedia Commons)



The wheel arrangement was also used on a number of small 0-4-0 diesel and gasoline engine-powered switchers produced by Whitcomb, Plymouth, Porter, and other builders beginning in the 1920s. Many of these were sold for industrial use.

There are 0-4-0 diesel-electric locomotives too, although small in number. The smallest diesel switchers, such as the EMD Model 40, were of this arrangement.

These small locomotives have been nicknamed "critters".