一楼理解的并不是很准确,正确的分析如下:
one the day before out departure,several bus loads of tourists descended on the town.
several bus loads of tourists 表示‘几车游客’
该表达来源于:a bus load of tourists;
several和a是用来限定load数量的,而bus是修饰load的定语;
类似的用法还有(注意load的单复数和它前面的限定词):
a car load of passengers 一轿车乘客;
several train loads of passengers ‘几火车乘客’;