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Old 03-17-2010, 04:17 AM
 
Location: San Diego, California
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Default What US interstate highway has the steepest grade, and where?

Does anyone happen to know? I've been searching online to try to find out but I've yet to come up with a conclusive answer.

I'm guessing I-84 in Oregon coming down/up Emigrant Hill...but I'm not sure. I think that one is at around 7% or so...which seems lower than what I'd assume the maximum would be, but IDK.

Anyone know the answer?
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Old 03-17-2010, 04:27 AM
 
Location: Cold Frozen North
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I've seen 7%. It was somewhere on I-80 in Wyoming. I think it was between Cheyenne and Rawlins. I don't know if there is any interstate with a grade greater than 7% - at least I haven't seen it.
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Old 03-17-2010, 05:41 AM
 
Location: Hernando County, FL
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Siskiyou Pass on I-5 in Oregon is supposed to be the steepest.

I-24 in Tennessee is not as steep but runs at a 4-6% grade for a long distance.
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Old 03-17-2010, 06:54 AM
 
Location: The land of Chicago
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I think the Interstate standard is no higher than 7 or 8%
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Old 03-17-2010, 07:32 AM
 
Location: Atlanta, GA
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The one on I-24 in Tennessee use to be a 9% years ago, but due to some many accidents, they rearranged the highway around Monteagle in order to bring it down to a 6%. Going up is about three miles, and coming down is four. They added an extra mile coming down so that they could cut into the deadly grade.
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Old 03-17-2010, 08:44 AM
 
Location: Ventura County, Ca
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It's not an interstate, but US 101 freeway in Ventura County, Ca is a 7% grade and I read somewhere that it's the steepest in California.
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Old 03-17-2010, 09:34 AM
 
Location: 38 38' 45" N, -90 20' 08" W
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I've driven on quite a few Interstate highways, and two come to mind: the section of I-70 near the Vail Pass in Colorado, and I-8 west of El Centro California.
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Old 03-17-2010, 10:30 AM
 
Location: Salem, OR
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Can't tell you the exact location, but passing through the mountains just north of Los Angeles heading north on I-5 had a very steep prolonged decline heading towards the central valley of CA. Steepest I think I can remember on an interstate anyway.
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Old 03-17-2010, 09:41 PM
 
Location: pine tree monotony
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Quote:
Originally Posted by FloridaMD View Post
Can't tell you the exact location, but passing through the mountains just north of Los Angeles heading north on I-5 had a very steep prolonged decline heading towards the central valley of CA. Steepest I think I can remember on an interstate anyway.
The "grapevine" maybe?
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Old 03-17-2010, 10:18 PM
rah
 
Location: San Francisco
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^yup that would be the grapevine, which according to wikipedia is a 7% grade. it has lanes for trucks to take the hill slowly so that they don't lose control, and it's lined with runaway truck ramps for those trucks that do lose control.
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