Toy Car Track Clamp

Print Profile A 

This one is simple, strong and reliable with not additional moving parts. 

Ensure there are no remnants of support filament when sliding the pieces in together. 

Print Profile B
 

This is a bit of an experiment. It adds some flexibility to the angle of the track, with the use of hinges. 

Note: The print tolerance for friction fitting parts can come out a bit small depending on your choice of filament, in which case a drop of super-glue to lock it in place will do the trick. If you want things to just work, no fiddling - maybe choose Option A.