Fire incidents due to the increased road transportation of flammable materials are a concern for steel reinforced concrete road bridges and allied structures. Though these structures are more fire resistant than steel bridges, they do require a more detailed consideration in the provision of fire safety measures as design considerations and post-fire exposure response. This study presents a comprehensive examination of the structural damage and subsequent rehabilitation of the B112 Sarnia Road Grade Separation Bridge on National Route N2, following a severe fire incident resulting from the collision of petrol and diesel tankers in August 2015. The bridge sustained significant fire-induced damage, manifesting as concrete spalling and visible cracking. Through an extensive damage assessment, including visual inspections, ground penetrating radar (GPR), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and thermal imagery, the severity of the damage was evaluated. The fire-induced damage was seen predominantly in the concrete matrix, with observations of spalling, a change in colour indicative of high-temperature exposure, and microstructural alterations. This case study further presents the details of the access system considerations, repair objectives, methodologies, and performance testing, ultimately demonstrating that careful monitoring and a well-executed repair response can significantly extend the service life of fire-damaged structures and ensure future serviceability.