????? Degrees/Percentage of a road (traffic signals)

[TrustButVerify]

I was just doing some road surveys nowadays in Ireland, and I found these signals (200m away from each other, one was doing downhill, the other one going uphill, so, not the same slope).

It's curious one traffic signal is in degrees, and the other one in percentage.

I tried to measure the slope with my smartphone, but I rather think it was not a quite good measure... The app showed almost 9 degrees of inclination when measuring the slope showing 11%.

Here is the drill:

My laziness made me go to google to calculate the percentage/degrees ratio and I found something curious, and now I have a doubt about it:

On internet, several websites take 45 degrees as 100% slope, so, for example, 11% is 6.28 degrees.
From my experience, I was taking into account 90 degrees as 100% slope, so, 11% is 9.9 degrees.

So, 9.9 degrees is closer to my measurement, than 6.28 degrees. And actually, the slope looked like 10 degrees inclination.

CAN YOU PLEASE SHARE YOUR EXPERIENCE WITH THIS? WHAT WILL BE THE REFERENCE FOR THE PERCENTAGE TRAFFIC SIGNAL? 100% as 45 or 90 degrees?

 

[ACtrafficengr]

Grade is rise/run*100. A 100% grade means you rise one unit of measure (meters, foot, barleycorn, etc.) for every unit you move forward. So a 100% grade is a 45 degree angle.

My glass has a v/c ratio of 0.5

Maybe the tyranny of Murphy is the penalty for hubris. -

http://xkcd.com/319/