Obviously, a megastructure such as an arcology puts vast distances between places indoors, making it impractical for traditional "outdoor" transportation networks to exist in the structure (note I didn't say impossible, just impractical).

If yuo read Post 3 on structure, you'd see that most commuting would be up and down, on traditional elevators, a tried-and-true technology. However, lateral transit, across one level of the structure, becomes increasingly important the larger the structure gets.

While most lateral transit would likely involve walking (I imagine Segways might be popular with some), moving walkways might also be installed on some levels. Roadways would also need to be marked on certain floors, as machines (most likely similar to electric pallet jacks) would be needed to move large items or bundles of products to commercial locations. Small electric cars, or refitted golf carts, could be used on these roads for police and emergency vehicles.

These ideas are taken from my experiences going to the airport, which involves a lot of lateral transit to and from far-flung terminals. The environmental benefits of this are huge, almost replacing fossil-fuel based transportation with electric-powered transportation (and foot-powered) for a large number of people. It is one of the most significant reasons for building the structure, to make everything either close enough to walk to or accessible by quick, efficient clean transportation.

As for transportation to and from the arco itself, as I mentioned in a previous post the arco should be built on a passenger rail line and close to an expressway, allowing visitors to either arrive by train or drive and park. This is important as the uniqueness of such a huge structure might make it a sort of tourist attraction, the way many large buildings (Sears Tower, Empire State Building) have become because of their size. A lower-level parking garage would also be important to those who "live the arco life" on the weekdays and want to get away from it on the weekends.