Standard references used for the design and analysis of walkways; assume that pedestrian stream is unidirectional. But in reality, the pedestrian stream is bidirectional. In this paper, the main question is whether the main features of the pedestrian stream in uni and bidirectional mode are the same? So, in this paper, the effect of making flow bidirectional in the main flow characteristics and pedestrian behavior are investigated. The investigation is based on both experimental and empirical data that were extracted from videos taken from Isfahan sidewalks. Results show that, in same density, the pedestrian mean speed in bidirectional flow is more than unidirectional flow. Mean speed difference in two type of flow becomes more considerable when densities are more than 0.6. The mean speed in majority and minority pedestrian group in bidirectional flow with unequal directional ratio is compared. The results show that density of the people walking in the same direction have more effective roll rather than counter flow density in each pedestrian speed. In high densities, the pedestrian try to walk in the trajectory that pedestrian walk ahead of him to reduce conflict. It leads to lane formation. In this paper, these lanes are studied in different densities and ratios. It is observed that number of the lanes increased in bidirectional flows. Using empirical data, fundamental diagrams are drawn for uni- and bidirectional flows. Analyzing pedestrian speed in all sidewalks shows that speed entropy in unidirectional flow is more in comparison to bidirectional ones.
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