The frequency of public transport service is usually higher in the rush hour, and longer trains or larger vehicles are often used. However, the increase in capacity is often less than the increased number of passengers, due to the limits on available vehicles, staff and, in the case of rail transport, track capacity including platform length. The resulting crowding may force many passengers to stand, and others may be unable to board. If there is inadequate capacity, this can make public transport less attractive, leading to higher car use and partly shifting the congestion to roads.