According to past researches, private motorized modes always have higher external costs than others yet private motorized modes have been used more constantly than public transit.

• 从过去之相关研究中可知私人机动运输工具具有较高之外部成本，但从各国的都市交通现况来分析，私人机动运具之使用率却佔了相当高的比例。