If you add too many minecarts onto a small section of track, they will get into stack and stop moving. If the track is destroyed, the minecarts will all fly off into the air with a 45 degree angle. They will only stop when they have blocks in their way. If you push or enter the minecarts they will head off into another direction if possible.

Steps to reproduce:
1. Create a relatively small minecart circuit with both types of tracks.
2. Place large amounts of minecarts on circuit and give them a push.
3. Wait for minecarts to stop, and destroy the rail they are on. Minecarts should rush away in a straight path.

You will find the screenshots of the minecarts on and off the rails below.