First the parts that may to change.
The massive loop on the speed circuit.
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The Immelmann (also massive) that starts off the speed circuit. You can also see the cobra roll at the beginning of the techincal circuit.
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Finally the switching system at the station.
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I've wanted to do a coaster like this for years, but NL2 is the first tool I've had that gave me the tools to do it. The trains are scripted to start together, even if they don't arrive at the same time, each getting on a different circuit (currently referred to as speed and technical).
Once they are on their way, these 4 switches change position. When the trains come back to the stations, after finishing their circuit, they are shunted past the stations and get back on the main track on the other circuit. The yellow train runs the speed circuit and then the technical circuit. The red train runs technical then speed. In the picture the yellow train is going though the Zero G Roll at the end of the speed circuit and you can see the switches in position for it to go onto the technical.
I will probably change this layout a bit so it is more elegant. I had a better configuration inspiration this morning.