Progressive is a wholly owned

Progressive is a wholly owned subsidiary of Caterpillar. 

Progressive owns EMD. 

Exactly which locomotive you saw depends as there have been multiple units painted in the Caterpillar corporate scheme for marketing purposes.

Question is, was it a smaller switcher unit, or a large road power unit. 

They have the GP24b which is a Tier 4 locomotive

https://s7d2.scene7.com/is/image/Caterpillar/CM20210205-701a7-dac49

And they have the SD70ACe which #1201 was painted for cat.

https://s7d2.scene7.com/is/image/Caterpillar/CM20170824-32080-35033?$highres$

I'm not sure if they've done a 70ACe-T4 or anything else.

very interesting

I googled around and here's a pic of a big sucker!

Compare to steam.

That is indeed one huge loco. How does it compare to a Big Boy or other large steam engine? I mean, weight, horsepower and/or tractive effort, top speed, I know diesesals have more starting power, and steam usually had more fast speed and tonnage. But that monster looks massively powerful to me. ? How about drawbar pull. Back it up with a monster steam and see which pulls which - unless the couplers/drawbars fail! < just for grins>

Big Boy vs SD70ACE

Easy to look up:

Lengths are reversed

The SD70 is 74 feet long, and the Big Boy is 132 feet.

Another issue is starting tractive effort, where the SD70 really outpulls the Big Boy.  

Scott Chatfield 

that one looks about right.

that one looks about right. it was nb out of fresno. i was sb on hwy 99. was getting starting to get dark so i did not get much chance to look at it. forget anything about a photo.

That would be the

That would be the SD70ACe-T4.

Slightly different paint scheme. The 1201 I posted earlier. That has EMD' 101J 4 stroke diesel. It also has some other quirks like fabricated bogies and the return of the teardrop windows. They are super quiet compared to the emd and GE T3 LOCOMOTIVES. Was this on UP or BNSF? Up has their GE/Wabtec tier 4s running acroas the system, but they tend to congregate on I5 corridor trains as it makes it easier to keep their emissions agreement with California. 

SD70ACe-T4 length

The SD70ACe-T4 is a bit longer than the regular SD70ACe, at 76'8".

I5?  must be a los

I5?  must be a los angles thing.  as here in ca the up runs along hwy 99. no trains run on the west side of the valley were I5 is.

I5

Its called I-5 because the rail service competes with truck service on I-5.  Has nothing to do with where the tracks are located.

Actually it has exactly zero

Actually it has exactly zero to do with the trucks either. It's called the I5 Corridor, because the service region is Seattle to LA. AKA Interstate 5. The fact that it may be closer to 99 (99E) or even split off to climb the cascades vs. sticking to the Siskiyous is irrelevant. 

Technically the service region is Hinkle (which is super not on i5 to West Colton from a locomotive service perspective, but that's neither here nor there.