All cars that are not registered will be towed to the nearest impound lot.

Identify the relative clause

The relative clause for the statement is "defining relative clause"

Explanation:

A relative clause primarily has a subject along with a verb, but would not stand alone as a complete sentence, hence would have an adjective to be able to give more information about the sentence.

A defining relative clause is one which is well defined as it provides answer to questions such as "which, where, how".

Hence the above statement is a "defining relative clause".