The Pro-Neck-Tor (PNT) helmet was developed to reduce the incidence of cervical spine injuries in head-first impacts. By guiding the head out of the path of the following torso, the helmet reduces the compressive loads on the spine. It consists of an inner- and outer-shell that are connected by an internal guide mechanism. In an impact the mechanism deploys and guides the inner shell and head relative to the outer shell. The helmet is intended to induce extension in slightly anterior-to-vertex impacts, and flexion in slightly posterior-to-vertex and vertex impacts. A passive deployment mechanism was previously designed, but was not thoroughly tested. The objective of this work was to assess the functionality of the passive PNT deployment mechanism, and suggest design improvements accordingly. The selector mechanism was prototyped and tested in a drop tower. The impact platform was positioned at three different angles (-15°, 0° and 15°) to generate posterior, vertex, and anterior impacts. The mechanism deployed in the correct direction in the -15° and 15° impact conditions, but deployed incorrectly in the 0° impact condition. Additionally, the mechanism did not induce sufficient head rotation prior to head rebound to reduce the loads on the cervical spine. A multibody model of the experimental apparatus was constructed to determine how the impact forces were transmitted to the mechanism to initiate flexion or extension deployment. A dynamic analysis revealed that the net moment on the head determined the deployment mode. This moment was affected by loading from the torso. Ultimately, the deployment mode should depend only on the location of an impact on the head. A new selector mechanism was designed, which is capable of sensing anterior impacts according to the direction of the loading vector on the head. By default, the mechanism deploys in flexion. In anterior impacts a switch is triggered, which changes the deployment mode to extension. A computational model of this mechanism showed the mechanism deployed appropriately in anterior, posterior and vertex impacts. The mechanism also produced greater head rotation prior to head rebound than the passive mechanism. Physical prototyping of this mechanism is recommended in the future.