Would you tell me if “in the driveway” functions as adjectives in the sentence “The car is in the driveway”?

Question

From The McGraw-Hill Handbook of English grammar and usage, 320p

Adjective prepositional phrases are prepositional phrases functioning as adjectives to modify nouns. For example, in the sentence The car in the driveway belongs to my aunt, the adjective prepositional phrase in the driveway modifies the noun car.

In the NP, "in the driveway" modifies the "the car". Like the preceding, in a structure level The car is in the driveway, can we say that the prepositional phrase "in the driveway" moidifies "the car", or does it modify a linking verb "is"?

Answer 1

The car is in the driveway.

A prepositional phrase may be used as an adverb telling how, when, where, how much, and why and modifying the verb and sometimes an adjective.

In your sentence, in the driveway modifies* is telling where the car is parked.

*As @BillJ pointed out, it actually complements the verb to form a grammatically correct sentence.

Answer 2

[1] The car in the driveway belongs to my aunt.

[2] The car is in the driveway.

Preliminary point: we don't talk of ‘adjective prepositional phrases’. Adjective and preposition are two distinct word categories (parts of speech) that have their own functions such as a modifier or complement.

In [1], the expression “in the driveway” is a preposition phrase functioning as modifier of "car". It ascribes to "car" the property of being "in the driveway".

In [2] things are slightly different. Here the PP is not a modifier but a locative complement of "is". It must a complement because it’s omission would render the sentence ungrammatical.

Note than obligatory elements are always complements: they are required to complete the verb phrase.