Banked U-Turns

Maybe you could turn some curved walls on their side and put it along the track.

Or use some inclines and rotate each piece by like 5 degrees, all the way around.

 

Worst comes to worst, you could do it the same way its done there with wall, doubles. Other than that...I really can't think of another solution. Sorry.

 

If you're happy with an ok turn you can just make the turn angled up slightly like you did in the sandbox map. Real banked turns are much more complicated.

Spoiler

We'll use 2x4s as an example.
1. Place a block perpendicular to the direction you plan to go.
2. Place a second one in front of it.
3. Place a third block on the exact same coordinates as the first block
4. Move the block .2 right and .1 forward and .1 up
5. Angle the block so the front left and back right corners are directly above or below the corners of the block it is merged into. The front right corner should be pointing up, and the back left corner should be merged down in block 2.
6. Adjust the height of block 3 so the front left and back right corners are in the same place as the corners of block 2.
7. Place another block against the front edge of block 3.
8. Repeat steps 3-6 until halfway around the turn. Coordinate snap movements may vary.
9. Do the same thing from the other direction.

 

The easiest way to make a banked u-turn is by using a Dish from the 'Decorative' object list, its simple, cheap and effective. But if you want a more detailed u-turn I suggest piecing it together with smaller objects. A common trick that I use is to set a hill marker to the shape of a circle, and then I set its radius according to the size of corner I plan to build. It makes it much easier to forge a banked turn when you have an outline to work with. Then its just a matter of throwing objects down and phasing them into the right angles, something with a large flat surface works best.

Good luck!