On-site　observations　show　that　several　damages　have　occurred　in　CRTS　II　slab-type　bal-lastless　track　system,　such　as　crack　and　interface　debonding　between　different　structural　layers,　which　will　trigger　the　occurrence　of　some　failure　modes　of　CRTS　II　track　slab.　As　the　damages　are　the　prior　for　specific　failure　modes,　time-dependent　reliability　of　CRTS　II　track　slab　should　be　conducted　considering　the　uncertainties　associated　with　both　the　failure　mode　and　the　damage,　which　is　defined　as　the　conditional　time-dependent　reliabil-ity　in　this　study.　To　appropriately　express　the　causal　relationship　among　the　failure　modes　and　prior　damages,　a　conditional　limit　state　function　(LSF)　model　is　proposed　with　explicit　expressions　provided.　With　the　aid　of　the　proposed　model,　conditional　time-dependent　reliability　of　CRTS　II　track　slab　for　two　individual　failure　modes　are　investigated,　which　are　the　steel　yielding　failure　mode　under　longitudinal　cracking,　and　the　vertical　instability　failure　mode　under　interface　debonding.　Furthermore,　conditional　time-dependent　system　reliability　of　the　track　slab　has　also　been　analyzed　considering　four　safety　failure　modes.　The　advantage　of　the　proposed　method　is　that　prior　damages　have　been　accounted　in　es-tablishing　the　failure　criteria　and　incorporated　in　the　formulation　of　time-dependent　re-liability,　which　provides　a　general　formwork　for　structural　reliability　involving　the　causal　relationship　among　the　failure　modes　and　damages.　(c)　2021　Elsevier　Inc.　All　rights　reserved.