A Truck-Mounted Attenuator (TMA) is a device mounted on road maintenance vehicles, positioned at the rear to establish a buffer zone between the vehicle and the construction work area ahead. A numerical model of the TMA, consisting of a steel skin, steel frame, and origami aluminum honeycomb, has been developed. This model can be extended to larger-scale collision scenarios, particularly those involving real vehicle models. The substantial cost-effectiveness of having a validated numerical model enables automotive crash cushion designers to perform extensive testing through numerical simulations prior to standard impact tests. The study also explored the energy-absorption characteristics of origami honeycomb during the out-of-plane crushing process within the TMA. Numerical simulation results indicate that origami honeycomb offers a more stable folding process compared to traditional honeycomb. The findings of this research will assist transportation agency designers in the development of the next generation of vehicle-mounted crash cushions, thereby enhancing the safety of highway maintenance vehicles.