关于英语动名词、与分词问题
The State Administration of Work Safety says that 90 percent of the major road accidents in the past five years were caused by overloading,speeding,and overtired or wrong-way drivers.
请问：
第一、“speeding”,“overloading” 为什么是动名词?“overtired ” 为什么要用分词呢?
第二、overtired 变成overtiring 为什么