In 2011, a study by the City of Ottawa showed that after students at Carleton University and the University of Ottawa adopted the U-Pass program, transit use increased by 39% and 35% respectively at the two universities. At the University of Ottawa, car use remained unchanged after the introduction of U-Pass thus the gains of transit use came primarily from students who walk/bike. On the other hand, at Carleton University, driving decreased by 33%. This raised some doubts at the University of Ottawa as to the environmental and social benefits of the U-Pass, considering that walking and cycling produces no pollution, whereas bus use causes pollution.