PURPOSES : The main purpose of this study is to identify directions for improvement of triangular islands installation warrants through analysis of the characteristics of crashes and severity with and without triangular islands on intersections. METHODS : The data was collected by referring to the literature and analyzed using statistical analysis tools. First, an independence test analyzed whether statistically significant differences existed between crashes depending on the installation of triangular islands. As a result of the analysis, individual prediction models were developed for cases with significant differences. In addition, each crash factor was derived by comparison with each model. RESULTS : Significant differences appeared in the "crash frequency of serious or fatal" and "crash severity" owing to the installation of triangular islands. As a result of comparing crash factors through the individual models, it was derived that the differences were dependent on the installation of the triangular islands. CONCLUSIONS : As a result of reviewing previous studies, it is found that improving the installation warrants of triangular islands is reasonable. Through this study, the need to consider the volume and composition ratio of right-turn vehicles when installing a triangular island was also derived; these results also need to be referred to when improving the triangular island installation warrants.

PURPOSES : This study proposes an index for analyzing mobility based on smartcard and taxi data to evaluate imbalances in public transit. METHODS : The proposed mobility index is calculated based on the difference between the mobility indexes of public transit and taxis using the variables of the in-vehicle time, waiting time, and driving ratio. For a more detailed analysis, the distances are divided into short distances, medium distances, and long distances. RESULTS : Public transit mobility indexes are generally evenly distributed, but the taxi mobility indexes are located in the largest legend. When comparing the respective mobilities of public transit and taxis, many areas with a high mobility of taxis (similar to the distribution) exist, especially in the outskirts such as Dobong-gu, Nowon-gu, Gangdong-gu, Guro-gu, Geumcheon-gu, and Eunpyeong-gu. On average, the mobility of public transit according to the distance is smaller in a short distance and higher in a long distance. CONCLUSIONS : The results demonstrate the use of the proposed index for analyzing the basic statuses of complementary indexes for evaluating public transit imbalances. In the future, more detailed results (including socioeconomic variables corresponding to the grid areas) should be studied to identify the impacts of the mobility index.