How do you get from Point A to Point C without traveling through Point B? Why you use a PPT Tunnel of course. In the end, it isn't much different from a wormhole. However, the way the Vuduri travel is somewhat amusing. They have to come to a complete halt relative to the nearest gravity well. They fire up their PPT generators and create a large pool of negative energy in front of them then they slide on through. The net effect is a velocity many times the speed of light but the actual speed to get there is very slow.
A PPT Tunnel begins collapsing as soon as you stop pumping negative energy into it. So a large ship must create a "wide" PPT Tunnel that will stay open long enough for it to get through. A smaller ship can create a narrower, but deeper tunnel. So larger ships cannot travel as far or as fast.
The controls within a spaceship have two controls. The first is for the width of the tunnel. It is usually a yellow wheel with a little triangular marker showing the "normal" position for a ship of a certain size. Within the wheel, a ring actually, is a pushbutton which controls the amount of negative energy pumped out. Thus a ship can control how far and therefore how fast by how deeply they create the tunnel.
Being able to travel faster than the speed of light is very important to a science fiction story that takes place within different solar systems. Otherwise, you'd spend the whole story just watching space go by.