What is the steepest grade in USA?
What is the steepest grade in USA? Waipio Valley Road on the island of Hawai'i is said to be the steepest rural road in the United States, with some grades approaching 45%. It has been closed to non-local traffic.
What is the steepest grade on I 80?
Most major U.S. highways don't exceed a 6 percent grade, the magic number for the preferred maximum steepness of a road. Parleys Canyon (I-80) has a maximum grade of 6 percent.