Dynamic Brake Support (DBS) is a safety system that has been applied to various passenger cars and has been shown to be effective at assisting drivers in avoiding or mitigating rear-end collisions. The objective of a DBS system is to ensure that the brake system is applied quickly and at sufficient pressure when a driver responds to a collision imminent situation. DBS is capable of improving braking response due to a passenger car driver's tendency to utilize multi-stage braking.Interest is developing in using DBS on commercial vehicles. In order to evaluate the possible improvement in safety that could be realized through the use of DBS, driver braking behavior must first be analyzed to confirm that improvement is possible and necessary. To determine if this is the case, a study of the response of truck drivers' braking behavior in collision imminent situations is conducted. This paper presents the method of evaluation and results.Data was drawn from a prior NHTSA simulator study and showed that many drivers exhibited multi-stage braking during four different imminent crash scenarios. Results from analysis indicate that a DBS system capable of detecting and intervening at the most conservative level of multi-staging presented could be successful in assisting drivers in avoiding or at minimum mitigating 30% of the collisions presented in this document. Further opportunities for assisting drivers based on reducing brake application time are also shown to exist. These results suggest that a DBS system may be valuable for heavy vehicles.