The Pennsylvania Railroad's steam locomotive class D2 (formerly Class B, pre-1895) comprised twenty 4-4-0 locomotives intended for mountain passenger helper service, constructed at the railroad's own Altoona Works (now owned by

Norfolk Southern The Norfolk Southern Railway is a Class I freight railroad in the United States formed in 1982 with the merger of Norfolk and Western Railway and Southern Railway. With headquarters in Atlanta, the company operates 19,420 route miles (31, ...

) during 1869–1880. They were the second standardized class of locomotives on the railroad and shared many parts with other standard classes. This design differed from the Class A (later D1) mainly in its smaller drivers for greater

tractive effort As used in mechanical engineering, the term tractive force can either refer to the total traction a vehicle exerts on a surface, or the amount of the total traction that is parallel to the direction of motion. In railway engineering, the term t ...

in mountainous terrain. Like all the early standardized 4-4-0s on the PRR, the Class B had a wagon-top boiler with steam dome and a

firebox Firebox may refer to: *Firebox (steam engine), the area where the fuel is burned in a steam engine *Firebox (architecture), the part of a fireplace where fuel is combusted *Firebox Records Firebox Records was a Finnish record label based in S ...

between the two driving axles. In 1881, the PRR took the Class B design and modified it to produce more locomotives for express passenger service, with drivers like the earlier Class A. These new locomotives were designated Class B A, and were classified as D2a in the post-1895 scheme; forty-five of them were constructed.

References

{{DEFAULTSORT:Prr D02 4-4-0 locomotives D02 Railway locomotives introduced in 1869 Scrapped locomotives Standard gauge locomotives of the United States Steam locomotives of the United States