- Zion simply bans private vehicles during the summer peak season. Bryce Canyon's shuttles are not mandatory.
- Zion's shuttles run until about 11:00pm. Bryce Canyon's end at about 6:00pm, which during the summer is before sunset, a most popular time to see the park.
- Zion's shuttles pull up right next to attractions. Bryce Canyon's park farther than the private vehicles.
Zion's mandatory policy is obviously the easiest way to achieve this, and a ranger told us they saw more wildlife just three days after the mandatory shuttle service was instituted in 2000. However, even if you don't want to force people to take shuttles, you should make it advantageous to take the shuttle. For example, the shuttle should take you closer to attractions than cars can. Make them walk. Run the shuttle through sunset, because you actually have a view point called "Sunset Point"!
We saw the same thing flying back to Oakland. The ground transportation roads to the airport are separated into three lanes, the closest one for private car drop-offs and pick-ups, the second for taxis, and the third for buses (including the AirBART bus that connects to the BART rail system). This is completely backwards, if you're trying to encourage the use of more efficient public transportation. The AirBART and other public buses should take me closest to the door, right off the curb. Private shuttles can take the next lane, and private cars and taxis should be farthest.
Now, this is not about punishing private cars. This is about allocating a scarce resource (walking distance) in a way that encourages desirable behavior. As long as it's more convenient to drive, people will do so.