Complex sentence: Each highway has ramps that exit to the other highway ending at an intersection that one can travel either direction--odd because both highways end up having at-grade intersections albeit with a grade-separation of the main highway corridors.
Split into simpler sentences: Each highway has ramps that exit to the other highway ending at an intersection that one can travel either direction. This is odd because both highways end up having at-grade intersections, albeit with a grade-separation of the main highway corridors.