Policies for on-board crowding in public transportation : a literature review

Crowding in public transportation is increasingly perceived as a problem in large cities. Public transport authorities strive to develop policies that manage demand and reduce crowding in the best way. This paper reviews studies of policy instruments aimed at crowding and demand management of public transportation, mainly quantitative studies. The most observed policies are adjustments of fare (including differentiation), frequency, capacity, bus size and in some cases road tolls. The reviewed studies either implicitly represent crowding by the willingness to pay for less crowding or by reduction of occupancy levels. We subdivide papers into studies that model transport scenarios and studies that observe passenger demand, often real-world cases. We use social welfare optimization as reference point for analysis of the study contributions. Studies that observe passenger demand present results limited to the effects on overall demand and generally not in terms of social welfare. Some studies report on price differentiating policies that succeed in reducing peak demand, reductions ranging from 1.2 to 10 percent. Most modelling studies find it optimal for occupancy to decrease, however, some studies find that higher occupancy rates are welfare optimal. Few of the reviewed studies present the costs and benefits directly associated with decreasing occupancy. Few studies present both spatio-temporal distributions of occupancy and include a policy for the reduction of crowding. This suggests that a clearer picture of the severity of on-board crowding, together with a policy to manage crowding would be useful.