One plane is the 15 to 20 foot reverse grade toward the uphill road portion and outlet. Another plane is the grade from the top of a hump or start of a down grade to the outlet of the dip. Neither the dip nor the hump should have a sharp, angular break. They should be rounded to allow a smooth flow of traffic. Properly constructed board-based dips do not damage loaded trucks, or slow vehicle speed.
Dips require minimal annual maintenance and continue to function years after abandonment.
Only the dip should be outsloped to provide sufficient break in grade to turn the water.