Rating hills - percentages??

Perhaps interstate but many state highways are more. I was on an 8% Sunday that was more than 1 1/2 miles (West Virginia). But yeah, makes sense for major highways be regulated for truck runaway issues, maybe.

Step Down said:
Is it true that all major high ways and interstate highways in the US are required have a max gradiant of no more than 6%? I have heard this for years from fellow cyclists. They say it's some kind of[size=-1] US Department of Transportation, Federal Highway Administration requirement.[/size]
The maximum of 6% applies only to interstate highways; however some exceptions have been granted in the mountains where it was not fesable to stay under 6%.

Historically, railroad beds could be as steep as 5%, but the preferred maximum for new construction is 1.5%, and the limit is 2%, unless a waiver is granted. Railroads also have a "ruling grade" which is calculated by the grade and distance and determines the maximum weight a locomotive can pull. The ruling grade is usually less than the maximum grade, because the train's momentum would be able to carry it up a 3% grade for a short distance, but it would not be able to sustain more than a 1.5% grade.
The only grade above 6% I could locate on the interstate highway system is a 5 mile section at 7% on I-64 at Sandstone, Virginia. The 6 mile incline on I-77 at Fancy Gap, Virginia, which can be fairly frightening in heavy traffic, is only 4.5%. The 6 mile hill on I-40 at Black Mountain, North Carolina is 6%. Here is a link to the trouble spots for truckers: http://www.zafr.com/trucktcom/grade.htm
With the exception of Sandstone, all of these are 6% or less.