ZOHRAN MAMDANI, New York's leftie(左翼的；左派) mayor, campaigned on the promise to make them free. They already are for residents of Tallinn, Estonia’s capital, and in several French regions. In Germany they were at one point so heavily subsidised that they might as well have been.(在德国，公交一度获得巨额补贴，几乎等同于免费。) Voters love them—and so do politicians, especially populist ones. Free buses, or extremely cheap public transport in general, are all the rage(风靡一时；十分流行). They are also terrible economics.
纽约左翼市长佐兰·马姆达尼在竞选中承诺让公交免费。在爱沙尼亚首都塔林以及法国多个大区，公交早已免费。在德国，公交一度获得巨额补贴，几乎等同于免费。选民喜欢免费公交——政客也喜欢，尤其是民粹主义政客。免费公交，或者说整体上极其廉价的公共交通，眼下风靡一时。但它们在经济上也是糟糕透顶的政策。
Advocates of the idea proffer(提出；提供) three main arguments. First, fares discourage use, raising the system’s cost per passenger. This in turn may lead to underinvestment and, as a consequence, a sparse and low-frequency service that is not as economically efficient as it could be.(这又可能导致投资不足，进而造成班次稀疏、频率低下的服务，其经济效率无法达到应有水平。) Lowering the cost barrier encourages ridership(乘客量；乘坐率), a denser network and a better service for everyone. Second, free transport takes cars off the road(减少上路汽车；让汽车少上路). Because motorists do not pay the full social cost of congestion(拥堵；堵塞), pollution and other “externalities(外部性)”, they do too much motoring. A zero-cost alternative makes even socially underpriced(定价过低的) car journeys less attractive, cutting traffic and accidents or making room for trees and playgrounds. Third, low or no fares make it easier for poorer households and non-motorists(非驾车者) (including the young, elderly and disabled) to participate in public life(参与公共生活). They also promote physical activity (ie, walking or, if you see your bus about to leave the stop, sprinting).(免费公交还能促进身体活动（即步行，或者，如果你看到公交车正要离站，那就冲刺）。) That is free public transport as social policy.
这一主张的拥护者提出三大理由。第一，票价会抑制人们使用公交，从而抬高系统的人均成本。这又可能导致投资不足，进而造成班次稀疏、频率低下的服务，其经济效率无法达到应有水平。降低费用门槛能鼓励更多人乘坐，形成更密集的网络，为所有人提供更好的服务。第二，免费公交能让汽车少上路。由于驾车者并未支付拥堵、污染及其他“外部性”的全部社会成本，他们开车开得太多。零成本的替代方案会让本就定价过低的驾车出行更不具吸引力，从而减少交通流量和事故，或为树木和游乐场腾出空间。第三，低票价或免票价让较贫困的家庭和非驾车者（包括年轻人、老年人和残障人士）更容易参与公共生活。免费公交还能促进身体活动（即步行，或者，如果你看到公交车正要离站，那就冲刺）。这就是作为社会政策的免费公共交通。
All three arguments have merit(优点；价值). But none of them justifies giving public transport away for nothing(把公共交通白白送出) or nearly nothing. Take economic efficiency. For this to rise, subsidised schemes would have to increase ridership substantially. Yet evidence on the ground(实地证据；实际情况的证据) suggests that their effect on passenger numbers is at best marginal(充其量只是微乎其微). In other words, public transport turns out to have what economists call low price elasticity of demand.(换句话说，公共交通的需求价格弹性很低——这是经济学家的说法。)
这三大理由都有其道理。但它们都不能证明应该把公共交通白白送出，或几乎白白送出。以经济效率为例。要提高效率，补贴方案必须大幅提升乘客量。然而实地证据表明，它们对乘客数量的影响充其量只是微乎其微。换句话说，公共交通的需求价格弹性很低——这是经济学家的说法。
There is no such thing as a free bus
世上没有免费的公交