Noob UP locomotive question

Greetings.

I have done what I can to search the forums but I cannot find the answer to my question. (If someone can point me to the answer, I would be grateful.)

Every so often I drive by the Davidson Yard in Fort Worth were dozens of UP locomotives can be seen, each with a three- or four-digit number on the side. The most common seems to be 3xxx, followed by 5xxx and 9xxx. Is the first one or two digits of each locomotive's number representative of some sort of classification, or are the number simply serial? If there is a significance, is there a decoded list?

Thanks in advance.

here is a fairly recent UP roster by road number. http://www.thedieselshop.us/UP.HTML
they are grouped by manufacturer and model, with a few exceptions, but there is no other significance to the numbers.

Those are locomotive road numbers..
each locomotive on the same railroad will have a unique road number.
but numbers can and do vary significantly between railroads..
you could have a Union Pacific number 8001 (just to pick a random number)
http://www.rrpicturearchives.net/showPi ... ?id=700024

that would be a completely different type of locomotive from BNSF 8001.
http://www.rrpicturearchives.net/showPi ... id=1588842

Some railroads once based "road number series" on horsepower or other locomotive characteristics..
Locomotives of 3,500 horsepower might be numbured in the "3500 series", 3501, 3502, 3503, etc..continuing for as many
locomotives in the class..but you dont see that much anymore simply because Class-1 railroads have grown so huge and have thousands of locomotives.

One locomotive can also change its road number several times in its career..with the same railroad,
or when it is sold to a different railroad..

and the same number can also appear on different locomotives on the same railroad, at different times.
as a group of locomotives is retired, the same numbers might be re-used on new locmotives of a completely different type..
the only "constant" is that one railroad will never have two locomotives with the same road number, at the same time.
other than that, the sky is the limit when it comes to assigning road numbers..

Scot

There are some small railroads which assign road numbers with the horsepower in mind.
The Providence & Worcester in New England is one such:
2006 to 2011 are 2000hp EMDGP38's
2201 was a GE B23
3004 to 3008 are GE B30's
3901 to 3908 are GE B39's
and 4001 to 4005 are GE B40's

Such a plan can work with a fleet of 20 engines, but UP has thousands.
As yet no North American railroads have gone to five digit numbering systems , though that's common in the rest of the world.