Breakaway supports are common devices used for dual support signs located along the roadway. Design of these systems often involves several costly vehicle crash tests to ensure their effectiveness. It is believed that mathematical modeling can be used to help develop new sign systems in a more timely and cost-effective manner. To this end, a dual support breakaway sign system was successfully modeled using LS-DYNA3D, a nonlinear, large deformation finite-element package. Small component models were first constructed on critical parts of the breakaway sign system. The component models were compared with physical component tests to aid in the development process, as well as to validate the results. The components were then assembled into a complete system model. Very few changes were made in the complete sign model, because problems were worked out in component modeling. Results from two full-scale vehicle crash tests were used to validate the system model. With successful results, the model can now be used to study various sign modifications and configurations.