Introduction<br> Many previous studies have researched the characteristics of pedestrian flow and measured the values such as the flow rate, speed and density, on the basis of the investigations of pedestrian movements in urban streets, stations, theater and others, in normal situations. There is a case that their results were used for the estimation of evacuation time. However, Most of these studies did not research the pedestrian flow passing through an opening in a wide space such as a room or hall in architecture and a public passage. This paper focuses on the characteristics of pedestrian flow during passing through an opening in wide space in detail, using the experiment.<br> Purpose<br> This study aimed to identify the characteristics of pedestrian flow during passing through an opening in wide space under a range of the opening width. The effect of an opening width on the pedestrian flow during passing through the opening in a wide space was elucidated, on the basis of the each transition of the specific flow [person/m/s] and walking speed [m/s], density [person/m²], and the walking trajectories.<br> Methods<br> The experiment was conducted on subjects walking and passing through the opening in the 6000-mm wide space. The experimental conditions were varied according to the opening widths and the distances between the opening and the start position of the subject crowd. The opening widths were set to one of the six levels under a range from 800 mm to 2400 mm The distances between the opening and the start position of the subject crowd were 1200 mm and 6000 mm. The number of trials in the distances of 1200 mm and 6000 mm were 3 and 1, respectively, in each level of opening width. The experiment consisted of 24 trials on the basis of combinations of two experimental conditions. The 96 non-handicapped subjects, all walked and passed through the opening in each trial.<br> Results<br> The parts of results of this study are as follows:<br> 1. When the opening width was multiples of 600 mm, the specific flow in the case that the distance between the opening and the crowd are 1200 mm and 6000 mm, were the same.<br> 2. When the opening width is multiples of 600 mm but that is 2400 mm, it is assumed that the walking speed and the density during passing through the opening in the case of 6000-mm walking distance to the opening are higher and less than those in the case of 1200-mm, respectively.<br> 3. The specific flow in each case that the distance between the opening and the crowd are 1200 mm and 6000 mm, were not much difference between the opening widths from 800 mm to 2400 mm. The averages in the case of 1200mm and 6000mm were 2.59 person/m/s and 2.49 person/m/s, respectively.<br> 4. When the width of the opening is from 800 mm to 2400 mm, it is assumed that the specific flow in steady state is about about 2.40 person/m/s at minimum.<br> Conclusions<br> This study set out to derive the characteristics of the transition and the steady state of the pedestrian flow during passing through the opening in the wide space. The results obtained will be useful for calculating the time for people to evacuate in the event of fire, using mathematical expressions or computer simulation.