Here is the central city of Bowden. I'm now on year 500 or so on the Maxis time. This is main commercial center of the entire region and also has thousands of high-tech jobs. From every direction, sims commute to and from Bowden daily. I ran the traffic querry tool and will post the numbers later if you are interested.
The downtown area is "inside the loop." There are a couple other areas where skyscrappers were built, but for the most part the outlaying area are medium and low density structures. The western and northwestern areas were built last, consequently those areas have a rail system. In the downtown area there is an extensive subway system that expands to some highly dense areas outside the loop as well. Most sims drive using the highway system, which has one major north/south interstate (I-95) and two major east/west interstates (I-10 and I-30) all intersecting around the loop ("Loop 110").
Around other parts of the region, there are smaller state highways connecting the cities and interstates together.