In preparation for the New York Extension, PRR built some experimental electric locos ,
borrowed at least one New Haven electric, and ran them against steam.
The conclusion was that symmetrical wheel arrangements increased lateral impact at the rail,
with highest impacts produced by the PRR and NH B-B motors.
PRR decided to produce the DD-1 i.e.; 2-B+B-2, or two D16s back-to-back.
Sam Vauclain patented a B truck with an additional, idler axle, and OA&E bought it too, albeit DC and smaller wheels etc than the New Haven version.
Twenty+ years later, PRR apparently forgot the lesson and built several O1, lots of P5 and one R1,
all of which were symmetrical and rode poorly. Some adjustments were made , but PRR again went to NH and borrowed a 2-C+C-2 which convinced them to design and build the GG1.
You folks that are trying to picture a GG1 whizzing thru the prairies STOP IT