Final answer:
The question seems to involve transportation law, but the provided details relate to physics about a truck on a hill. Without information about state regulations, an accurate answer about vehicle height restrictions cannot be given.
Step-by-step explanation:
The question refers to the maximum height allowed by state law for a vehicle, including its load. However, the provided information regarding a truck having a mass of 1.2 tons and moving down a hill that is 150 meters high suggests the topic is related to physics. In physics, this scenario would typically examine concepts like potential energy and kinetic energy, as well as motion and forces. Unfortunately, the provided information does not include specifics about state law restrictions on vehicle heights. These regulations can vary significantly by location and would fall under the subject of law, not physics. Without the legal information pertaining to vehicle height restrictions, an accurate and informative response to the specific query cannot be provided.