Learn Italian: È importante rispettare i limiti di velocità. - It is important to respect speed limits.

In Italian, you don't use a subject pronoun like "it" for impersonal expressions. You just start directly with the verb, so è importante simply means "it is important." This works exactly like the verb bisogna (it is necessary), which also stands entirely on its own.

Why isn't there a preposition before rispettare? Doesn't it mean "important to respect"?

In English we need the word "to," but in Italian, impersonal expressions of necessity like è importante, è necessario, or bisogna are followed directly by the infinitive verb. You do not add a or di before rispettare.

Why is the plural of limit i limiti?

The singular noun for "limit" is il limite. Even though it ends in -e, it is a masculine noun. Like almost all Italian nouns ending in -e, it changes to -i in the plural, taking the standard masculine plural article i.

Why does Italian use di in limiti di velocità?

English often stacks nouns together to describe things, like "speed limits" or "water bottle." Italian doesn't do this. Instead, you connect the two nouns with the preposition di (of), literally saying "the limits of speed."