[Makid]

Is the idea to reduce vehicle use by encouraging transit or is it to improve transit without being a detriment to cars?

Here in Salt Lake City, the LRT line (Trax) runs in the center of the various streets in a dedicated ROW. The sections south of the Downtown area and into the southern suburbs all operate in a separate ROW. Even the primary East/West tracks run in the center of the street until the line is close to the airport (west) & university (east).

This did lead to a change in behavior:

Prior to the opening of the initial line in December 1999, approximately 15% of Downtown workers used Transit. Today, nearly 28% use transit for their commute to Downtown Salt Lake. Additionally, the University of Utah when from around 10% transit share to nearing 40% transit share (extension opened in December 2001).

While the idea of an underground section may sound good. Think of the additional service that you could get elsewhere with the ground level option. Additionally, as the system needs to expand it will be cheaper and easier to add additional spurs and extensions.