I think the bottlenecks on UP around Elko are a result of directional running on to separate rights of way. Years ago the Southern Pacific and Union Pacific (IIRC) had separate rights of ways between Winnemucca and somplace in eastern Nevada or Western Utah. There is a control point east of Winnemucca called Weso where the two rights of way split going east bound. They parallel each other but are often miles apart. The rights of way are on opposite sides of a river as they pass through several canyons between Winnemucca and Elko. There are few places where trains can switch from one track to another. So if an eastbound freight breakdown in front of 6, 6 will be delayed. If a WB freight breaks down in front of 5, then 5 will be delayed.
I use an app called GPS tracks, which allows one to download maps ahead of time so you can have GPS access on your iPhone even if there is no cell signal. You can zoom in on these maps to see the alignments of the two separate rights of way. It is pretty cool once you understand what is going on.
I am not an expert on this, and Union Pacific which now owns both rights of way should not be criticized based on my understanding of operations. I probably do not have all of the information.