The contact owns a 2018 Toyota Prius. The contact stated while driving approximately 5 MPH and in heavy traffic, the contact depressed the brake pedal for traffic but the brakes failed. The contact stated no warning light was illuminated. The contact crashed into the rear end of a truck. The damage was very light due to the low speed. The top of the hood at the front was scratched and the grill also sustained minor scratches. The contact continued on the road. The contact had taken the vehicle to a local dealer, who contacted a manufacturer representative to diagnose the vehicle. The contact was advised that there was no brake failure. The vehicle had not been repaired. The manufacturer had been informed of the failure. The failure mileage was 40,063.