Occupant protection of vehicle cab is required for all the commercial vehicles. According to ECE R29-03 amendments, the simulation methods of the front pillar impact test and the side 20 o pendulum impact of the roof strength test for a light truck with a gross mass not exceeding 7.5t are proposed. In this study, a reliable finite element model of a light truck is built by using its CAD model. The finite element model is verified against cab modal test and frontal impact test. Then two crash tests are simulated to evaluate the survival space by examining the contact between the deformed cab and a prescribed manikin model. In the front pillar impact test, the deformed cab is predicted to contact with the manikin. In the roof strength test, the minimum distance between the deformed cab and the manikin is predicted to be 75.3 mm, which does not satisfy requirements either. To enhance the crashworthiness of the truck, some structural improvements are designed such as filling structural foam in the A-pillars and the side panels, adding a roof crossbeam, and reinforcing the rear wall of cab. The simulation results of the improved cab structure show that the cab stiffness is improved, the energy absorption is more homogeneous and there is no penetration into the survival space.