UTAH National Parks

The tunnel is inside Zion NP on route 9. The picture below from Google Earth shows the switchbacks on the approach to the tunnel coming up from Springdale. The line marking the road ends at the tunnel entrance at the middle of the picture and reappears near the right edge about half way up.

Thanks Gonzo42, can you tell me where the tunnel entrance is? Specifically is it where 89 & 9 meet or is it on 89 after the 89/9 junction. My plan is to drive to Virgin, so I want to go from 89 to 9 and wondering if that still forces me through the tunnel

Only issue with grades and switchbacks is going to be the approach to the tunnel in Zion and the tunnel itself. Check the Zion NP website for restrictions. They will charge a fee for the permit restrictions on length or height as they close the tunnel down for one way traffic. Many many rv's go through there daily just depends on your specific rig if it fits
https://www.nps.gov/zion/planyourvisit/the-zion-mount-carmel-tunnel.htm
other than that 9 is fine a bit narrow within the park, 89 and 12 are fine roads and should present no real issues to Cannonville. In fact only other significant grade I can recall is 12 coming down off the plateau by Bryce to the valley bottom and again the road is fine.

In the summer time the tunnel they typically just close traffic one direction for a period of time last one through takes the baton to the other side gives it to the ranger and then traffic is allowed to go the other direction for x period of time or until they run out of waiting vehicles and again last person through takes the baton back to the other side. I have never had to wait more than 15-20 minutes at the height of summer traffic though it has been about 5 years since I was there last.

Was there last week. I almost did that route until I found out about the tunnel and the switchbacks. You have to pay $15.00 and be escorted through the tunnel and you also have bad switchbacks. The tunnel was cut in the 30s and is only 13 feet high in the center. Traffic is escorted one way at a time, you must be in the center of the road, and the time it takes is more than if you went up I-15 to exit 95 (route 20) and go through Panquitch to the 89.