In 1938 GE built two steam turbine locomotives for the UP. I've seen the wheel arrangement listed as 2-C-C-2 on a number of pages. Wikipedia lists it as 2+C-C+2. Which one is correct?

https://en.wikipedia.org/wiki/GE_steam_ ... ocomotives

This is the GE classification for the two locomotives: 2-C-C-2-530/548-6GE725B

These locomotives do not have an articulated underframe, like a PRR GG1: they have pin-guided four-wheel lead trucks and cast three-axle underframes, but there is a full-width set of tanks between the inner ends of the underframes.

Lionel Wiener's 'taxonomy' for articulated locomotives uses the "+" to denote an articulated hinge between frames -- as for the GG1, which is a 2-Co+Co-2 (using the European convention of appending the lowercase 'o' to a group of powered axles to denote that they are independently and not gang-driven). (Those of a certain age will remember Bob LeMassena's somewhat quixotic effort to make us all observe the same convention for Mallet-chassis locomotives -- because there is a hinge between the main frame and the forward engine.)

Wikipedia is simply, stupidly, utterly wrong: it is difficult to conceive why anyone would make a 2+C-C+2. Perhaps Mr. Wales & Co. propose to revise Whyte coding for every locomotive with a pin-guided lead truck, using a novel interpretation unsupported by Wiener; I can't explain any sense or reasoning otherwise.

Call it a 2-C-C-2, just as GE did, in the United States.