I oftentimes see how our moderators warn speed demons against overly aggressive itineraries, and I can repeat their caveats from personal experience.
If you are going to take the time to visit the National Parks, I recommend setting aside adequate time to see them. When I see fellow members planning on seeing Bryce and Zion in the same day before heading back to Las Vegas, I have to wonder what the use is in simply driving through the parks without stopping for more than 10 minutes.
During the late spring to early fall the parks are CROWDED. To go from point to point in Zion you have to take a shuttle bus. While they run frequently, they make it impossible to drive quickly through the valley and jump out for a few minutes at a time to snap photos. Most of the parking lots at Bryce were full from about 10:00 AM, so it takes a while to find a place to park and see the sights at Sunset Point and popular areas. The line at the visitor center information desk was long, and it took us 15 minutes just to get the Junior Ranger workbooks. Slow down and enjoy the scenery and information at hand!
The roads between the parks are oftentimes slow going. It can be hard to adjust from driving 75 MPH on certain sections of I-15 to being stuck behind a truck on US-89 or UT-12 on a twisty road at 30 MPH. Don't plan on averaging 60 MPH on rural roads or you'll end up behind schedule and frustrated. I grew up in a family that did the kind of drives our moderators warn against (e.g. leaving So' Cal' in the evening one night and not stopping for an overnight rest until we got to Seattle the following night), but I am committed to making realistic plans and not trying to cram too much into my itinerary. I include time for the kids to get out and stretch their legs, see the sights, buy a couple of souvenirs, and take a dose of ice cream. This keeps my family from loathing road trips.
Thanks for sharing that. I can guarantee that the Mods will be citing this post to future road trip planners!
Mark