There is a route outside Fillmore Utah, it is called chalk Canyon road (some maps call it chalk creek).
You would exit off of I 15 at exit 167 if coming from Salt lake go into town to 200 South St and turn left, coming from Arizona still exit 167 exit take a right at the exit curve around into town and take right on 200 south. You will see the mountain range out of Fillmore. 200 will turn into Chalk canyon road which turns into willow creek road. I think there is a sign at this name change point as it makes a hard turn to the right makes a hard turn to the right.
I am not sure and pics did not take so not sure. I think at this point the road splits three ways and Willow creek continues on to the right and comes out on I-50 after nine miles. There is also a sign that says road not maintained and suggest 4 high clearance vechicle and heavy duty tires. If you take this route it is fairly rough ,we did it in a mazda miata and came out no problem. If the weather is bad rain or snow or ha sjust done so I would not go this second route because of no way to trun around and possible rock slides and it is slippery when wet. If you do go proceed with caution as the road gets very narrow . Taking the willow creek road I would think would be fine in bad weather we did not try it so can't say. Both roads will come out on I 50 and the thrid one dead ends
You can travel the chalk road and willow road for some distance with no problem and it is a great drive.
We saw a lot of different animals as well as trout swimming in the stream by the road.
If you have time spend a day or two in Fillmore and look around there is some great sites and roads all over the place. I would suggest a GPS as well if you get off the beaten path. Before driving any road in the area including the Chalk,I would go by the forest ranger station get a map and check road conditions.
We did see some 4 wheelers and 4x 4 trucks up in the area and they did look at us funny in that small convertiable . Feel free to contact me if you have questions maybe I can help