A year and 4 months ago we drove US-431 south from Central City, KY where we'd visited some rv.net forum friends and on south thru Russellville, KY and on to I-24 to connect with I-65 at Nashville on our way to Florida. We were pulling our 12,800 lb Carrilite 5th wheel.
Sure would like to know where that steep hill is because all we saw was rolling land and basically farms/farm lands and nothing steep or a long grade that's remotely worrying. Most of the road distance was very smooth and divided road areas and nice travel.
They were resurfacing one area but that was over a year ago. Our friends in Central City (is the ex-mayor of the city for 12 years) suggested we go that way south so we did and they were right as there wasn't a lot of traffic and was a nearly straight shot to I-65.