为了缓解拥堵、治理环境，机动车限行在越来越多的城市日益常态化。政府通告对机动车使用进行限制是对公民私有财产权的减损，私有财产权属于公民基本权利，对其进行限制必须要有法律授权并且通过合宪性审查。机动车功能实现因其所具有的社会关联性，存在一定的社会义务。本文对机动车限行常态化的形式正当性和实质正当性进行了分析，单双号限行属于私有财产超限的社会义务，不构成实质征收。机动车限行常态化缺乏明确的法律依据，不符合适当性和必要性的要求，在机动车对大气污染影响的科学结论缺失的情况下，难以通过比例原则的审查，因此机动车限行常态化有违宪之嫌。国家对公民基本权利进行限制的行为必须具有宪法正当性，否则宪法的尊严难以树立。

To ease the congested roads and control air pollution, traffic restriction is getting normalized in many Chinese cities. The government's announcement in which restricted the use of private cars has limits on private property. The ownership of private property as one of the fundamental rights of citizens, limits on which should have legal reservation and pass the constitutional review. Private property with high social relevance, such as private cars, has its own environmental obligations to the society. Yet traffic restriction based on the odd and even number is an over-limit obligation. With analysis of both formal and essential legitimacy, the normalization of traffic restriction lacks legal reservation, appropriateness and necessity. Meanwhile, the principal of proportionality cannot be met with the absence of scientific verification between the use of motor vehicles and polluted haze. Therefore, the normalization of China's traffic restriction violates the Constitution. Limits relate to people's fundamental rights should be strictly constitutional. Otherwise, the dignity of the Constitution can hardly be built.