There's a very steep narrow road in the swiss Alps with 27 % height difference in the wineyards just northwest of Ardon in the center of the canton of Valais, in SW Switzerland. It is called Route de la Vallée.
27% is really steep. No problem when the road is dry or just wet from rain. But in winter it gets icy... and since it is very steep, it gets very dangerous to drive on, especially downhill, because of the car's weight pulling you downhill. Many accidents happen on this road in winter.
Here I drive down on it... there's not much ice anymore except in a few specific places where the road is very steep... sometimes I drive up there in an SUV and still put snowchains on all 4 wheels, for better grip and control. Drove this road up and down in december with over a foot of fresh snow .
Here in this video I don't have the snow chains on my car, there is almost no more ice and snow but still a few icy slippery zones... and the car, a Toyota RAV4 , has amazing downhill steep electronic braking control.. you can hear the brake system take control rather loudly but safely.. I don't touch the brakes, I let the car do its thing... despite the narrow steep road with patches of ice.

filmed with a smartphone dashcam-style in ultrawide cinematic view.