Train passes underneath itself - GIF

[Frank S]

How many cars were there? what do you mean about 1° grade?

Here you go Ralph
https://en.wikipedia.org/wiki/Tehachapi_Loop
A good read.the actual slope is an average of 2.2%. However, I want to point out for any who are not aware of the differences between gradient elevation degrees and percent of grades. Which falls into another of those measuring confusions. 1% of slope is 2° of angle. A 45degree angle is 100 percent slope
This will to better understand
https://en.wikipedia.org/wiki/Grade_(slope)