  Crowding in train cars is increasingly a major concern for transit agencies.
From the perspective of the passengers and the transit agencies, overcrowding
of the train cars has several negative consequences such as: (i) extended
duration of passengers boarding and alighting which leads to longer dwell
times, (ii) subsequent disruption of the headway and the schedule, and (iii)
passenger dissatisfaction (e.g. increased stress and lack of privacy).
Moreover, overcrowding during peak service hours also indicates inadequate
infrastructure to meet the passenger demands. Realizing the importance of the
crowding issue, transit agencies have developed measures to assess the crowding
levels. The Transit Capacity and Quality of Service Manual provides guidelines
on thresholds for crowding in transit systems in the United States.
