Because of this winter's National Parks TV documentary, the projection is that interest in the parks will be increased. Last year, because of the economy, park visitation was up. With those two things still in effect, expect crowded roads. If you have travelled the road, you know how narrow it is in parts. Also auto drivers are looking at the scenery and not paying good attention to their driving.

Having said that, I think you would be alright if you hit the park entrance at dawn and planned to be over the top well before noon. We used to enter at that time, early enough that the booth was unattended and there was no line of cars to get in. We'd see lots of wildlife and few cars until around 10am. A lot of people on vacation tend to sleep in. Many times as we left the park at 10 or 11am, we'd pass long lines of cars waiting to get in. Downside is, mornings can be very cold that high up in the mountains.