摘要
直到现在，许多人仍然抱有一种普遍存在的观点，即市区公共交通只有两种可供选择的方式：公共汽车或常规轻轨（有时也称有轨电车）。但是，两者都存在不足之处。公共汽车污染环境，同时效率低下，消耗的能源多；常规轻轨除了应用在人口极为密集的大城市之外，在一般的城市的使用成本太高。
Acommon assumption up until now has been that there are only two alternative forms of urban public transport to choose from - buses or conventional light rail, sometimes called trams. But there are disadvantages to both. Buses pollute and are inefficient energy consumers. Conventional light rail has become too expensive for all but the larger cities, where populations are at their most dense.
