It 100% has to be a block brake in order to run 3 trains.
Speaking of block brakes, I was thinking about it, and I came up with this.
Since there is no block brake on the blue track (between the blue and green lift hill), doesn't the green lift hill train have to release first, that way in case there is an E-stop, two trains won't occupy the green lift? Sorry if this is confusing, but hopefully someone sees what I'm going at.