Pennsylvania Railroad

Pennsylvania Railroad

The Pennsylvania Railroad was an American Class I railroad, founded in 1846. Commonly referred to as the "Pennsy", the PRR was headquartered in Philadelphia, Pennsylvania....

's Odd D #10003 was an experimental electric locomotive

Electric locomotive

An electric locomotive is a locomotive powered by electricity from overhead lines, a third rail or an on-board energy storage device...

 built in 1907 of 4-4-0

4-4-0

Under the Whyte notation for the classification of steam locomotives, 4-4-0 represents the wheel arrangement of four leading wheels on two axles , four powered and coupled driving wheels on two axles, and no trailing wheels...

 wheel arrangement

Wheel arrangement

In rail transport, a wheel arrangement is a system of classifying the way in which wheels are distributed beneath a locomotive.. Several notations exist to describe the wheel assemblies of a locomotive by type, position, and connections, with the adopted notations varying by country...

 in the Whyte notation

Whyte notation

The Whyte notation for classifying steam locomotives by wheel arrangement was devised by Frederick Methvan Whyte and came into use in the early twentieth century encouraged by an editorial in American Engineer and Railroad Journal...

, or 2-B in the AAR

Association of American Railroads

The Association of American Railroads is an industry trade group representing primarily the major freight railroads of North America . Amtrak and some regional commuter railroads are also members...

 scheme. On the PRR, class D was assigned to 4-4-0 locomotives. Production classes of locomotive were assigned a number after the letter, but one-off locomotives were simply designated "Odd".

In testing, #10003 proved to be more stable at speed than the two class AA1

PRR AA1

The Pennsylvania Railroad's class AA1 comprised two experimental electric locomotives constructed in 1905 by Westinghouse at the start of the PRR's electrification project.They were testbeds for larger locomotives to come...

 B-B locomotives the PRR had also constructed, so its 4-4-0 arrangement and high center of gravity was chosen as the design for the PRR's DD1

PRR DD1

The Pennsylvania Railroad's class DD1 were semi-permanently coupled pairs of third rail direct current electric locomotives built for the railroad's initial New York-area electrification. They operated between Manhattan Transfer and Pennsylvania Station in New York City, and from there to the...

production locomotives.