When doing some testing with Minecarts, I setup an commandblock to TP a minecart to me (for picking up Shulkers), I accedently got into the cart and once it landed on the ground it just went straight through until eventually clipping the Bedrock and sending me falling into the void.
I dont think thats suppost to happen, is it?
However, in order to recreate do the following.
1.Set up an Commandblock and connect it to a redstone clock [faster clocks give faster results as the minecart is teleported more oftenly]
(or in 1.9 just set it to repeat and always active).
Command:
/execute @p ~ ~ ~ /tp @e[r=10,type=MinecartRideable] @p

Step 2. Place/spawn an ordinary Minecart and get inside.
(Tip: use gm3 once below bedrock to avoid the annoying part dying)