How do you make backwrds accel lines?

Well....To change the acceleration direction, follow these instructions!
1-Choose the red acceleration lines
2-choose which ever tool you want
3-HOLD "SHIFT"
4-Make the line by dragging it to the left instead of the right...WHILE HOLDING SHIFT!!!
While the rider rides across the line a force will push him the opposite way that he's going...Good luck