How do I stop the train in chapter 3?

In chapter 3 of Half-Life: Alyx, there's a section where you need to stop an incoming train. After hacking the control panel, a lever appears that breaks off when you try to pull it. Now Russel keeps telling me I need to look for a switch instead.

Where do I find the switch to stop the train?

You need to go outside that room and follow the train tracks until the junction where the rails diverge (it is close, so don't go far away). From there at your right, you should see an elevated platform with some steps, go there. There's a yellow lever (or switch) that you need to pull and keep pulling until the train passes because it won't stay in place.

Check this video.