I have been to Denali, there are no cars allowed in the park, there is a bus system that runs thought the park.
I have heard rumors that MRNP is looking into doing the same.
Imagine: parking your car at the entrance to the park waiting for a bus, loading on the bus with up to 40 other people and your pack, riding a bus up to Paradise with no shocks, and then doing the same back down. So much for cold alpine starts if the bus does not run early.
It works very well at Denali, but I am hesitant for MRNP to start.