The combined pressure-decay technique with rheometry is developed to measure the diffusivity of carbon dioxide (CO2) in bitumen at temperatures of 30, 50, and 70 degrees C and pressures of 2 and 4 MPa. Mixing due to shear imposed by a rheometer allows rapid direct measurement of the equilibrium pressure in CO2 bitumen systems accurately. The comparison of the measured equilibrium pressures with the values obtained from the data regression demonstrates significant discrepancies, which can lead to a great deviation in the diffusivity, up to 5-fold different than the true values. The measured values for the diffusivity of CO2 into the bitumen increase with temperature, following the Arrhenius equation. By changing the temperature from 30 C to 70 degrees C, the diffusivity increases by 88% at 2 MPa and 54% at 4 MPa. The diffusivity also increases with the pressure, suggesting the ease of diffusion at the presence of the CO2 molecules in the liquid phase. The effect of pressure is more dominant at lower temperatures while the diffusivity increase is 53% at 30 degrees C, compared to 25% at 70 degrees C. Furthermore, the findings demonstrate that the CO2-bitumen system does not follow any constant pattern in the diffusivity-viscosity-temperature relationships, which is due to the ongoing phase change at the studied temperature range.