Proponents of the Mobility as a Service concept claim that subscriptions to alternative modes can effectively reduce car ownership and the adverse effects of underpriced car use. We test this hypothesis in a microeconomic model with endogenous mode choice as well as car and subscription ownership. The model contains congestible urban rail and car sharing options as substitutes of underpriced private car use. We find that aggregate car ownership is not a reliable proxy for road congestion: subscriptions may reduce car ownership while increasing the vehicle miles travelled by remaining car owners. Subscriptions induce welfare losses for two reasons. First, pass holders overconsume the alternative modes, as the marginal fare they face drops to zero. Second, non-pass holders tend to shift to car use due to the crowding induced by pass holders, causing additional distortions. We illustrate numerically that differentiated pricing is more efficient in achieving the goals of MaaS.

移动即服务的支持者概念声称，订阅替代模式可以有效减少汽车拥有量以及低价使用汽车的不利影响。我们在具有内生模式选择以及汽车和订阅所有权的微观经济模型中检验该假设。该模型包含拥挤的城市铁路和汽车共享选项，以替代低价私人汽车的使用。我们发现总的汽车拥有量并不是解决道路拥堵的可靠方法：订阅可能会减少汽车拥有量，同时增加其余汽车拥有者的行驶里程。订阅会导致福利损失，原因有两个。首先，通行证持有人过度消费替代模式，因为他们所面临的边际票价降至零。其次，由于通行证持有人引起的拥挤，非通行证持有人倾向于转向汽车使用，从而导致额外的变形。