intersection at the crossroad is located a considerable distance from the main facility,
then both ramp and mainline roadsides should have independent designs, until the
slopes merge near the gore.
If the quadrant is entirely, or nearly so, in cut, the combination of a 3:1 backslope
at the low roadway ditch and a gentle slope down from the high roadway shoulder will
provide the best design in the wide portion of the quadrant. Approaching the gore, the
slopes should transition to continuous 4:1 and 6:1 or flatter slopes. Quadrants located
entirely in fill areas should have independently designed roadways for ramp, mainline,
and crossroad. Each should be provided with normal slopes not greater than 3:1, with
the otherwise ungraded areas sloped to drain without using ditches. If the quadrant is
located part in cut and part in fill, the best design features a gentle fill slope at the upper
roadway and a gentle backslope at the lower roadway, joined to a bench at the existing
ground level that is sloped to drain. The combination of a long diamond ramp having
gentle alignment with a loop ramp in the same interchange quadrant is not to be treated
as a trumpet. Each ramp should be designed independently of the other in accordance
with the suggested details set forth above.