Measuring Transportation Accessibility

对交通可达性的衡量

How transportation is defined and measured can affect which solutions are considered best.A particular policy or project may appear worthwhile when transportation system performance is measured in one way，but undesirable when it is measured another way.

通行能力如何被定义和衡量会影响到最优方案的选择。在某种标准下，一项特定的政策或方案可能看起来很有价值，但是当以另一种方式进行衡量时，可能毫无意义。

Conventional transportation often reflects the assumption that transportation means motor vehicle traffic.From this perspective，anything that increases motor vehicle traffic speed and volume improves transportation，and anything that reduces motor vehicle traffic speed and volume must be harmful.

在我们大脑中传统的交通运输概念通常是指机动车交通。以这样的理解来看，任何能够提高机动车通行速度和交通流量的措施都会改善交通能力，而任何降低机动车通行速度和流量的措施必定是有害的。

A more comprehensive approach reflects the assumption that transportation means personal mobility，measured in terms of person-trips and person-kilometers.From this perspective，strategies such as better transit services and rideshare programs may improve transportation without increasing total vehicle-kilometers。However，this approach still assumes that movement is an end in itself，rather than a means to an end，and that increased personal movement is always desirable。

一种更深入的理解反映出这样一种假设：交通意味着人的流动性，可以用人次和人公里数来衡量。如果从这个角度来理解，诸如更好的公交服务和乘坐共享等策略可以在不增加车辆总里程数的情况下改善交通。然而，这种理解仍然是假设流动是其本身的目的，而不是达到目的的手段，并且认为增加人的流通量总是可取的。

The most comprehensive definition of transportation is Accessibility：the ability to reach desired goods，services and activities。This is the ultimate goal of transportation，and so is the best definition to use in transportation planning。It recognizes the value of more accessible land use patterns and Mobility substitutes such as telecommuting and delivery services，as ways to improve transportation while reducing total physical travel。

对于交通最全面理解的定义是无障碍：即到达所需的物品，服务和活动的可能性。这是交通运输的终极目标，也是应用于交通规划的最佳定义。它认识到更容易通达的土地利用模式和代替移动行为的服务（如远程办公和交付服务）的价值，作为提升有效交通量同时减少实际出行总量的方法。

Many transportation projects improve Accessibility by some modes，but degrade it for others。For example，increasing roadway capacity and traffic speeds tends to improve Access by automobile，but reduces it by other modes such as walking，cycling，and transit。Only by defining transportation in terms of Accessibility can these trade-offs be considered in the planning process。

许多交通项目通过某些模式改善了可通达性，但是也因为其他模式降低了可通达性。例如，增加道路容量和通行速度往往会改善汽车的通行性，但是却降低了步行，骑车和穿越性交通等其他模式的通行量。只有通过对交通可通达性术语的准确定义，这种利弊才可能在规划中加以权衡考虑。

Vehicle traffic is relatively easy to measure，so the evaluation of transportation system quality tends to be based largely on automobile travel conditions（such as average traffic speeds，roadway level of service，vehicle congestion delay，vehicle operating costs，parking supply），while ignoring other Accessibility impacts，including impacts on transit service quality，nonmotorized transport，and land-use Accessibility。This tends to favor automobile-oriented solutions，and undervalues alternative solutions to transportation problems。

机动车交通相对容易测量，因此交通系统质量的评估主要基于汽车行驶条件（如平均交通速度，道路服务水平，车辆拥堵延误，车辆运营成本，停车位供应等），而忽略了可通达性的其他影响，包括对公交服务质量，非机动交通和土地使用可达性的影响。这往往有利于以汽车为导向的解决方案，却低估了解决实际交通运输问题的其他替代解决方案。