AbstractCollision of overheight vehicles into bridge superstructures often leads to structural damage, posing an immediate risk to the safety of motorists and the functionality of bridges. Considering the proven vulnerability of current high-strength concrete (HSC) girders to impact-induced forces, the use of ultrahigh-performance concrete (UHPC) (to fully or partially replace HSC) is expected to improve the impact resistance of bridge superstructures. However, despite the growing attention that UHPC has received for various bridge applications, this important application has remained largely unexplored. This motivated the current study to perform a holistic investigation to (1) quantify how the performance of bridge girders subjected to overheight collision can be improved by a one-to-one replacement of HSC with UHPC; (2) assess how UHPC can be considered as a material of choice for repairing existing bridge girders impacted by overheight vehicles; and (3) examine how equivalent UHPC girders designed for a performance similar to HSC girders under service loads can introduce advantages when subjected to overheight collision. For this purpose, upon validating a set of finite-element models with experimental test results, numerical simulations are performed on two types of AASHTO girders. The simulations cover two impacting objects, i.e., a concrete conduit pipe and a cylindrical steel tank, in addition to a tractor–semitrailer. The structural performance measures of the bridge girders made of HSC (entirely), UHPC (entirely), HSC repaired with UHPC, and equivalent UHPC are then evaluated and compared based on the recorded damage patterns, impact forces, internal shears, and lateral displacements. The outcome of this study provides the necessary details to shed light on how a transition from HSC to UHPC can contribute to improving the overall safety and performance of new and retrofitted bridges, especially when subjected to overheight collision.