This shot shows the driver's door bars. Notice the two vertical braces supporting the bars right at the location of the driver's hips and legs. You could use less tubing (and save a little weight) by connecting the braces to the bottom bar, but Leavitt points out that this won't help the driver much. In the event the driver takes a hard hit from another car right in the side, that car's bumper will probably hit right about the second bar up. That's why these braces are there.