  Individual differences in mobility (e.g., due to wheelchair use) are often
ignored in the prediction of crowd movement. Consequently, engineering tools
cannot fully describe the impact of vulnerable populations on egress
performance. To contribute to closing this gap, we performed laboratory
experiments with 25 pedestrians with varying mobility profiles. The control
condition comprised only participants without any additional equipment; in the
luggage condition and the wheelchair condition, two participants at the center
of the group either carried suitcases or used a wheelchair. We found that
individuals using wheelchairs and to a lesser degree those carrying luggage
needed longer to pass through the bottleneck, which also affected those walking
behind them. This led to slower times to fully clear the bottleneck in the
wheelchair and luggage condition compared to the control group. The results
challenge the status quo in existing approaches to calculating egress
performance and other key performance metrics in crowd dynamics.
