We have some absurdly long (3-4.2km) freight trains in Canada, and they go through systems like this all the time. You can see the front of the train at the top

We have some absurdly long (3-4.2km) freight trains in Canada, and they go through systems like this all the time. You can see the front of the train at the top of the mountain while the bottom is still going in! https://en.wikipedia.org/wiki/Big_Hill https://en.wikipedia.org/wiki/Big_Hill https://en.wikipedia.org/wiki/Spiral_(railway) https://en.wikipedia.org/wiki/Spiral_(railway)