||Vehicle traffic control has been introduced as a countermeasure to over-use in various natural parks of Japan. Users' understanding is indispensable for enforcing vehicle traffic control. Thus, the present traffic control system must be examined based on an evaluation from the viewpoint of visitors. Kohgen area of Daisetsuzan National Park and Kamuiwakka area of Shiretoko National Park in Hokkaido (northern island of Japan) were chosen for case studies. Data were collected by a mail-back questionnaire survey for visitors of these areas in 1999–2001. The results showed that most visitors approved or supported the traffic control systems. Approval ratings of vehicular traffic control were closely related to the visitors' acceptability of inconvenience by the control. The visitors' acceptability of the inconvenience was closely related to the length of period under the vehicular traffic control, and interval between shuttle buses. The parameters of the investigation included the timing of the survey. Approval ratings were higher within the restriction period than outside. The study confirmed that there were some elements to which the relationship to the traffic control approval were steady or unstable according to the investigation year. This finding strikes a note of warning about discussing significance levels from data acquired over a single year.