In the near future, drivers are expected to face vulnerability under the takeover phase in automated cars of level 2 or 3. We focused on the problem resulted from decreased vigilance and difficulties in shifting attention while drivers take over the control from the automatic mode. In order to address this problem, we explored 'VACT (Visual Assistance Concept for Takeover)', which applies dynamicity to shift visual attention. From a thorough literature review, we have come up with two windshield interface concepts to enhance drivers' vigilance and readiness before the takeover: Useful Field of View (UFOV) and Object-View (OV) Interface. To evaluate the UI concepts, an in-lab experiment was conducted with 57 participants in a semi-naturalistic driving environment. Implications for interface design of visual assistance and its impact on brake reaction time, mental workload and perceived usefulness are discussed.