<p>As the critical structural member in cable-supported bridges, cables must be safeguarded when subjected to vehicle fires due to their vulnerability at high temperatures. Previous studies broadly adopted a uniform radiative thermal boundary layer on the cable surface, leading to inaccurate predictions of the performance of bridge cables in fire. This paper proposes a novel theoretical method for computing the spatial heterogeneous radiant heat flux on the external surface of bridge cables in vehicle fires. The scheme geometrically discretized the flame and cable surface and then derived a closed-form view factor from an arbitrary position on cylindrical surfaces to the radiating flame face that was geometrized into multiple quadrilaterals. Validated by complex cases, this method is effective in appraising the heterogeneous radiation distribution on the fire-exposed bridge cable surface. Case studies were then performed on a cable-stayed bridge wherein a truck fire occurred near the stay cables and on a suspension bridge whose cable system was exposed to tanker pool fires. The calculated high-resolution radiant heat flux demonstrates that its heterogeneity is prominent axially and circumferentially. Superficial locations facing the flame receive the peak radiation, and the back heat exposure is zero. The resulting thermal boundary conditions for bridge cables more accurately represent real-world conditions, enabling more precise investigations of their thermomechanical response in the future.</p>