Grade Percentages
 

I suppose this question would relate to towing. How is the percentage obtained when referring to hill steepness? What is it a percentage of?

Re:Grade Percentages
 

I have tried to find that answer also....I use to carry a degree guage in my truck to date the steepest upgrade I have found was 16* upgrade but it was on a township road and not marked with a sign other then a street sign ( Goat Hill Road )<br><br>Grade Percentages I am sure are figured by the highway dept based on length of upgrade compaired amount of rise ???

Re:Grade Percentages
 

I agree. I always thought the grade was a ratio of rise over run. If the road rises 5 feet up per 100 feet of roadway, the grade would be 5%.

Re:Grade Percentages
 

Yep, ratio of rise to run. The steepest one I have found officially marked is from Apple valley up to Big Bear- The back way. (Southern CA) Marked at 16% grade.

Re:Grade Percentages
 

[quote author=03ho link=board=11;threadid=13700;start=0#129097 date=1050597961]<br>Yep, ratio of rise to run. The steepest one I have found officially marked is from Apple valley up to Big Bear- The back way. (Southern CA) Marked at 16% grade.<br>[/quote]<br><br>Thats my old play ground!<br>Born and raised in Apple Valley.<br>Used to make that trip (the back way) frequently to do some camping/4wheeling up in Big Bear.<br>Theres a couple of switch backs on that road that are steeper than anything Ive seen before or since.<br>Its officially designated as Hwy 18.<br><br>Ahhh, the good 'ol days. :)<br><br>Rich

Re:Grade Percentages
 

100% grade would be a 45 degree angle.<br><br>http://www.howstuffworks.com/question380.htm

Re:Grade Percentages
 

Thanks for the info guys! I've always wondered how it was measured.

Re:Grade Percentages
 

Sonora Pass in Ca has a short 26% section. I will be going over it as soon as the snow is gone and they open the road.

Re:Grade Percentages
 

[quote author=03ho link=board=11;threadid=13700;start=0#129097 date=1050597961]<br>Yep, ratio of rise to run. The steepest one I have found officially marked is from Apple valley up to Big Bear- The back way. (Southern CA) Marked at 16% grade.<br>[/quote]<br><br>Yep pulled 84,000 pounds up that thing once. Had to get around the scale at Cahone. Tad steep, thought I was going to have to call a wrecker then the crest came ::)

Re:Grade Percentages
 

Jeez you guys, do us Canucks have to teach you everything? ??? % grade is based on the number of trucks that can't climb the hill without a running start. So the steeper the hill (or the more F**** and C****** registered in the area) the higher the percentage. [eyecrazy] If'n yer gonna give answers, give the correct answers dangit. ;D Rick

Re:Grade Percentages
 

&quot;100% grade would be a 45 degree angle.&quot;<br><br>HMMmmm - *I* woulda thought, a 100% grade would require a 90 degree angle, or straight up....<br><br>But math was never my strong subject... ;) ;) ;)

Re:Grade Percentages
 

North-South Rd in our county has 2 miles of 21% down-grade leading to campgrounds. Lots of RVers wish they had read the sign before starting down. Especially when they start to leave. Calling a tow truck in the forest where cell phones don't work is not an easy task.

Re:Grade Percentages
 

Gary, if you picture a right triangle with the vertical and horizontal legs being equal distance (rise over run 100%) the hypotenuse (road surface) is rising at a 45 degree angle. ;)

Re:Grade Percentages
 

I was at a popular amusement park in Northern CA a couple years ago, and one of the rides was one of those 240' vertical drop things. In all the hype you see while waiting in line, one hokey road sign they have posted says &quot;100% grade&quot; I just laughed when I saw it, but nobody else seemed to get it. This was &quot;Drop Zone&quot;, not &quot;45* angle zone&quot;. [eyecrazy] [eyecrazy]<br><br>-SFB<br><br>ps They also have a ride called Top Gun, and whoever painted the mural put F-15s on the carrier deck, not F-14s. [eyecrazy]

Re:Grade Percentages
 

&quot;Gary, if you picture a right triangle with the vertical and horizontal legs being equal distance (rise over run 100%) the hypotenuse (road surface) is rising at a 45 degree angle.&quot;

Perhaps, but it's been my understanding that grade percentages were arrived by the average vertical rise occuring in a forward travel of 100 feet - but even in the above scenario, what happens if the incline angle is increased MORE THAN 45 degrees - do you now have a grade angle GREATER than 100%?

Actually, *I* think a real-life 100% grade would be 90 degrees, in other words, 100 foot rise in 100 feet of travel - straight up - BUT, if I'm wrong, maybe one of the grade experts here will tell my what the grade percentage actually IS at 90 degress or straight up - is there a grade percentage GREATER than 100%

Is there a 150% or 200% grade? We have MANY slopes around here where I live that are greater than 45 degrees - are THEY *over* 100 percent grades?

The original question was:

&quot;I suppose this question would relate to towing. How is the percentage obtained when referring to hill steepness? What is it a percentage of? &quot;

Is it possible we are mixing 2 different methods of mathematical equations here, and that the one used by the various hiway departments differs from that used in our geometry classes? Percentage of GRADE, and degree of INCLINE might use differing methods or standards of calculation...

In any event, sometimes it pays to simply go to the source, so I've sent the question direct to DOT for their reply as to how they compute grade percentages - if we can't believe them, we can't believe anyone... ;) ;) ;)