204. By contrast, the risk of death for drivers between 30 and 59 decreases with each additional passenger.

英语四级译文:
与此相反，30到59岁之间的司机在载有乘客时出车祸的几率随着乘客的增多而减小。

四级词汇讲解:
本句的主干是the risk of death decreases。between 30 and 59修饰drivers;with引导伴随状语。

by contrast意为“相反”，相当于in contrist。如:
The coastal areas have mild winters，but by contrast the central plains become extremely cold.沿海地区的冬天天气暖和，而与此相反，中部平原却会异常寒冷。

英语四级考点归纳:
by contrast与in contrast含义相同，都表示“相反，大不相同”。与此含义相同的短语或者词汇还有on the contrary, conversely和oppositely，它们的区别在于:

※ by contrast与in contrast都只强调所比较的事物是不同的。如:
But, in contrast, it is only in modern times that Galiteo has become a problem child for historians of science.但是相比之下，对于科学史学家来说，伽利略唯有在现代才被看做是问题小孩。

※ on the contrary多用于观点或想法，暗示有很多不同方面的选择。如:
He is not poor, on the contrary, he is a millionaire.他不穷，相反，他是个百万富翁。

※ conversely暗示所比较的两者截然相反。如:
Describe your greatest accomplishment and why it is important to you and,conversely, your greatest disappointment and what you learned from that exprience.描写你最大的成就，并说明对你而言它为何重要，还要描写与此相反的你最大的失败经历以及从中得到的教训。

※ oppositely暗示所比较的两者之间矛盾突出而尖锐。如:
My plan for career is not single, oppositely，I tend to expand my work into diversification.我的职业规划不是单一的，相反，我倾向于在不同的领域中开拓事业。