Speed limit is one of the traffic problems in Hokkaido due to unreasonable speed limit for both summer and winter. Based on questionnaires, the opinions from more than half of examinees have shown that speed limit of the roads in Hokkaido is too low and should be different in summer and winter. Then, this study is introduced to adjust speed limit reasonably, depending on road characteristics and road conditions. In this study, Free Flow Speed (FFS) equation is applied to calculate the speed limit in summer. For speed limit in winter, FFS and Stopping Sight Distance (SSD) equations are used. Most of the drivers are satisfied with the results. Moreover, speed limit on a circular curve is adjusted by the minimum radius of circular curve equation. However, these results should be verified in terms of safety and traffic efficiency to obtain the optimal speed limit.