Test Track has been open first thing in the morning of an EMH in my experience. In fact, my BF and I went through that line, and even though it was so early nobody had made it through the make your car step of the standby line, and we were the first two people to reach the loading area, they still put us in separate cars. Was kind of funny to see our photos where we were each the only person in our cars. Now EE single rider line doesn't seem to open until the park has been open a while and the stand-by line has built up a bit.