"Don't think it's 18%. I think you're referring to the sign in this Google street view. But 14% is still a pretty decent grade."
I drove this road last April, the sign I referred to said 18 per cent grade steep curves next 4 miles. If you do not want to believe me, Frankly Scarlet...
I did not attempt to get off my bike and measure the grade but assume the state of Utah has better things to do than put up erroneous warning signs along their highways. :S
:R