...I was on my delivery route in midtown Sacramento near K Streets at the UP (ex WP) crossing at 20th street at about 9am when in my rear view mirror the gates dropped and UP 1983 crossed at a VERY slow speed compared to most freights, no more than about 10 mph. My jaw dropped when three UP passenger cars followed, middle one a dome, then UP 1996 brought up the rear, both diesels facing outwards in (apparently) push pull mode. UP 1996 was on the geographic north and UP 1983 on the geographic south end of the 3-car train. I never got close enough to get the specific passenger car types and/or car numbers. This train went back and forth between C Streets and N Streets, stopping and retracing its path about 5 times at least very slowly.

Any idea what this was?

Matt K