St George, UT to Cannonville, UT (Bryce Canyon Trip)

I would, and have, taken the road (UT-9) from Zion and straight through the tunnel to Carmel, then north on 89 to 12. That saves a lot of time and only costs $15 for the rangers at Zion to stop the traffic through the tunnels so only traffic going your direction is in the tunnel and you have the whole road to ride the centerline.

You can read the requirements for using the tunnel at https://www.nps.gov/zion/planyourvisit/the-zion-mount-carmel-tunnel.htm.