翻译：1.为了您的家庭幸福，务必遵守交通规则（要用到Do）

For your family's happiness, please do observe the traffic rules.
这里，“do”就是“务必”的意思。

For the happiness of your family, please do abide by the traffic rules/regulations

In order to your family is happy, observes the traffic regulations byall means must