Any model railroader knows about the Turnouts, it's a straight track with a switchable guide (can be mechanical or electrical) that also allows the train to exit into a turn. It's a way to expand layouts and have multiple paths.
For slot cars, I just finished my high speed oval track however there are times when more serious racers are present and I have an inner road course inside the high speed oval. Right now I have to detach/move/re-attach a few pieces to swap between the two race tracks.
If I had a turnout, then I wouldn't need to take anything apart and just set the guide rails to either have the cars continue straight through or have them exit into the road course. To add a bit of realism, when the cars are redirected onto the road course I can put up some guard rails or similar on the straight piece, just like they do are real race tracks.