One problem related to air brake has been reported for the 2006 Toyota Prius. The most recently reported issues are listed below.
I own a second generationprius (2006), and it has the same brake symptoms that are being described by the owners of the 3rd generation model. When I apply the brakes while going over a rough surface, the brakes do not engage for a second or two. This has been the case since I purchased the car new, and I thought it was just a quirky characteristic of the hybrid, so I have learned to compensate by giving myself an unusually large distance between me and the car ahead of me. This doesn't always work, as people cut in front of me when the gap is large. I have not been in an accident, but there have been several near-misses with me almost rear-ending the person in front of me due to this brake problem. I hope the NHTSA is looking at all models of the Prius for this defect. In my form below, I checked air and hydraulic brakes because there is not an option for anti-lock brakes on the drop down box.