% Grade vs Degrees

NewToy · May 15, 2006

Anyone know what the difference between % of a grade as opposed to how many degrees the grade is? I always see the signs on the hiway saying 5% grade and it sure seems awfully steep.

Thanks,
John

NewToy · May 15, 2006

Anyone know what the difference between % of a grade as opposed to how many degrees the grade is? I always see the signs on the hiway saying 5% grade and it sure seems awfully steep.

Thanks,
John

jinman · May 15, 2006

I believe % grade is a measure of the rise to the run or how much the roadway rises compared to the length. If a roadway rose 1' for each 1' of length, that would be 100% grade (or the same as 45°). A 5% grade would rise 1' for each 20' of length or about 2-1/2°. When you are looking into a grade, your perspective is distorted. If you looked at the grade from the side, it would look a lot less imposing.

Disclaimer: There is a good possibility that my explanation is completely bogus, it's just my own understanding or lack of same. /forums/images/graemlins/smirk.gif /forums/images/graemlins/laugh.gif

jinman · May 15, 2006

I believe % grade is a measure of the rise to the run or how much the roadway rises compared to the length. If a roadway rose 1' for each 1' of length, that would be 100% grade (or the same as 45°). A 5% grade would rise 1' for each 20' of length or about 2-1/2°. When you are looking into a grade, your perspective is distorted. If you looked at the grade from the side, it would look a lot less imposing.

Disclaimer: There is a good possibility that my explanation is completely bogus, it's just my own understanding or lack of same. /forums/images/graemlins/smirk.gif /forums/images/graemlins/laugh.gif

RobS · May 15, 2006

Percent grade is just the rise over run. A 45 degree slope is 100% as the rise and run are the same. Your 5% grade is 5 feet in 100 which calculates to 2.86 degrees. The formula is Angle = ATAN (Rise/Run).

If you think 5% feels steep, try that 100% grade sometime /forums/images/graemlins/smile.gif

RobS · May 15, 2006

Percent grade is just the rise over run. A 45 degree slope is 100% as the rise and run are the same. Your 5% grade is 5 feet in 100 which calculates to 2.86 degrees. The formula is Angle = ATAN (Rise/Run).

If you think 5% feels steep, try that 100% grade sometime /forums/images/graemlins/smile.gif

chili · May 15, 2006

Here is how I figure 5% grade. 5/100=.05. Then take .05 and inverse tan which gives you 2.862405 degrees. Hope this helps.

chili · May 15, 2006

Here is how I figure 5% grade. 5/100=.05. Then take .05 and inverse tan which gives you 2.862405 degrees. Hope this helps.

BubbaJr · May 15, 2006

Here's a LINK to a grade calculator.

BubbaJr · May 15, 2006

Here's a LINK to a grade calculator.

Bird · May 15, 2006

Looks to me like everybody got it right, but jinman and RobS figure it the way I would. I'd probably never remember "inverse tan" and Chili's method even though you get the same result. /forums/images/graemlins/laugh.gif

Bird · May 15, 2006

Looks to me like everybody got it right, but jinman and RobS figure it the way I would. I'd probably never remember "inverse tan" and Chili's method even though you get the same result. /forums/images/graemlins/laugh.gif

NewToy · May 15, 2006

I always see that "5% Grade Ahead" sign going through Virginia at Fancy Gap. That's when they start putting the "Runaway Truck" escape ramps along the road. It seems like it's steeper than that but I guess not.
Thanks fellas,
John

NewToy · May 15, 2006

I always see that "5% Grade Ahead" sign going through Virginia at Fancy Gap. That's when they start putting the "Runaway Truck" escape ramps along the road. It seems like it's steeper than that but I guess not.
Thanks fellas,
John

Bird · May 15, 2006

I don't remember where "Fancy Gap" is, but I do remember a grade of that much, or more, on I-64, and one of those escape ramps on I-77 in Virginia. But the most deceiving one I've driven on was (best I can remember) about a 6 mile stretch of 12% grade on the north slope haul road in Alaska. They named their slopes and that one was called "Beaver Slide". I have a couple of pictures of a truck, burned completely up, sitting at the bottom of that slope.

Bird · May 15, 2006

I don't remember where "Fancy Gap" is, but I do remember a grade of that much, or more, on I-64, and one of those escape ramps on I-77 in Virginia. But the most deceiving one I've driven on was (best I can remember) about a 6 mile stretch of 12% grade on the north slope haul road in Alaska. They named their slopes and that one was called "Beaver Slide". I have a couple of pictures of a truck, burned completely up, sitting at the bottom of that slope.

flwiii · May 15, 2006

Salt River Canyon on U.S. 60 in Arizona carries a 6% grade. I agree it looks much steeper that it measures in degrees. Are there any places with greater that 6% grades on U. S. Highways, excluding dirt roads in the back country? I seem to recollect a 7% grade somewhere in my readings, but don't remember where that was, or if I was just dreaming.

flwiii · May 15, 2006

Salt River Canyon on U.S. 60 in Arizona carries a 6% grade. I agree it looks much steeper that it measures in degrees. Are there any places with greater that 6% grades on U. S. Highways, excluding dirt roads in the back country? I seem to recollect a 7% grade somewhere in my readings, but don't remember where that was, or if I was just dreaming.

DaveNay · May 15, 2006

( Salt River Canyon on U.S. 60 in Arizona carries a 6% grade. I agree it looks much steeper that it measures in degrees. Are there any places with greater that 6% grades on U. S. Highways, excluding dirt roads in the back country? I seem to recollect a 7% grade somewhere in my readings, but don't remember where that was, or if I was just dreaming.
)

6% is the federal limit for interstate highways.

Of course....everything is subject to exception. /forums/images/graemlins/crazy.gif

DaveNay · May 15, 2006

( Salt River Canyon on U.S. 60 in Arizona carries a 6% grade. I agree it looks much steeper that it measures in degrees. Are there any places with greater that 6% grades on U. S. Highways, excluding dirt roads in the back country? I seem to recollect a 7% grade somewhere in my readings, but don't remember where that was, or if I was just dreaming.
)

6% is the federal limit for interstate highways.

Of course....everything is subject to exception. /forums/images/graemlins/crazy.gif