A physically-based 1-D heat and mass transfer model was tested to estimate the heat fluxes of an asphalt surface. The model was run for two summer months for a road test site in southwest Sweden. Parameters for thermal properties, surface runoff, radiation and turbulent transfer were obtained from a description of the road stratification and from the literature. Coefficients of determination (r2) 0.94, 0.93 and 0.97 were obtained when simulated results were compared with observations of net radiation, heat flow below the surface and surface temperature respectively, all with slope coefficients close to unity. In addition, simulation results elucidated the role of water vapour transport through the asphalt-soil profile and its effect on the latent heat flow from the surface. Problems were identified with closure of the heat balance in measurements based on discrepancy between simulated and observed sensible heat flux.