I was traveling on I-35 in heavy stop & go traffic, in an area under heavy construction where no shoulder was accessible, when the 18-wheeler in front applied their brakes consistent with the flow of traffic. I applied the brakes, but nothing happened causing me to roll forward and hit the back of the 18-wheeler. After impact, I placed the vehicle in park, & it was not until I pressed park that I believe the brakes became re-engaged. Once out of heavy traffic & safe to do so, I exited the highway, pulled over & restarted the vehicle. I believe the manual brakes failed to engage causing the incident. My safety and the safety of my passengers was put at risk, brakes are an integral part of a vehicle. I was not going fast and was actively engaged in driving. When I pushed the brakes and nothing happened, I repeatedly slammed my foot on the brake as my vehicle continued to roll into the 18-wheeler. Had I been going faster and a vehicle in front of me hit their brakes me and my passenger would be seriously injured. Toyota corporate has inspected the vehicle, and their response was as follows: "According to the electronic data, the brake pedal was being softly applied during the recorded event. The brake pedal was forcibly applied 1.05 seconds prior to the crash. The electronic data indicated that the brakes were never applied prior to the impact." I have attempted to speak with Toyota Corporate (Legal Claims & Brand Engagement Center depts.), but they have been unresponsive to my