Crowd dynamics has been attracting more and more attention in the past decades because of the serious accidents occurred within pedestrian crowds, especially near bottlenecks. In this paper, pedestrian flow features at bottlenecks, i.e. room exits, are investigated with human-experiments considering varying door sizes and locations. The measure of evacuation time all indicated that lager door widths showed higher egress efficiency. Our analyses showed that the time lapses between two successive pedestrians displayed heavy-tailed distribution in all the scenarios studied. Meanwhile, regardless of the physical setups, faster flow rate and greater burst sizes with the increasing door width were found. Moreover, the influence of the boundary layer, as well as the effective width on pedestrian crowd dynamics were clearly observed. Our results also demonstrated that the door position also has an effect on the pedestrian flow at bottlenecks. In narrow door scenarios, the specific capacity was continuously decreased from the middle exit scenarios to the corner exit scenarios. As the door width increased, this gap gradually disappeared.