Adverbial clause as antecedent of pronoun?

Question

Please consider the following sentence:

When cars collide, it creates a debris hazard on the road.

In a debate, I claimed the sentence is ungrammatical because the pronoun "it" has no antecedent. However, I was unable to find a rule in my 12th edition of the Gregg Reference Manual for "dangling pronouns."

The only noun in evidence is "cars," so the antecedent of "it" could, implicitly, be any one of the cars. The adverbial clause "when cars collide" could imply an instant in time, and "it" might refer to that time. However, I know of no rule that permits an adverbial clause to function as a noun.

Much more likely is that "it" refers to an implicit "collision," but there is no structure in that sentence that could even remotely serve as a concrete antecedent meaning "collision."

I lost my argument because I was unable to produce a grammar rule that disallowed the sentence. My opponent claimed that the meaning is clear. The meaning's being clear is a straw man, of course, irrelevant to the question whether the sentence is ungrammatical, but I lost the debate on votes.

My questions are, precisely:

1. Is the sentence ungrammatical?
2. If so, can one cite a rule that's violated?
3. Can an adverbial clause function as a noun, and thus as the antecedent to a pronoun like "it?"
4. If so, can one cite a rule allowing an adverbial clause to function as a noun? (ironic aside: I almost wrote "can one cite a rule allowing it," causing a nested instance of this very question).

Answer 1

I believe you have a simple case of the “dummy it” here. It doesn’t have an antecedent; it’s not meant to refer to anything.

Surely you would buy this as grammatical:

It’s bad when cars collide. (What’s bad when cars collide?)

And therefore this:

When cars collide, it’s bad.

Let’s try your sentence:

It creates a debris hazard on the road when cars collide. (What creates a debris hazard on the road when cars collide?)

When cars collide, it creates a debris hazard on the road.

We do this all the time. You can find some relevant results for when NOUN+ VERB , it VERB at the Corpus of Contemporary American English. (Click ALL FORMS (SAMPLE): 500 after the results appear to expand the examples.)

Here are a few spotted there:

And when Bruce surfaced, it surprised pretty much everyone.

When people meditate, it brings a certain sense of peace onto the campus that trickles out to other people.

When storms hit, it affects the righteous as well as the unrighteous.

When people volunteer, it helps their souls, it helps them socially, it helps them in business, and it helps the community.

Here are some the other way around it VERB NOUN+ when NOUN+:

It bothered Jerry when people acted strangely.

When you connect with a person and they say they’ll call you back, it produces anxiety when you realize (you’re) going to be gone for three days.

It made headlines when the most powerful member of the U.S. Senate clobbered America’s media giants.

She could see it angered Thang when Roi called her that, and Grandma's face would tighten whenever she heard Roi's callous laughter at Na's misfortune.

All that said, I think your sentence would sound better with a passive construction:

When cars collide, a debris hazard is created on the road.

Answer 2

It doesn't need a clear antecedent to be grammatical.

Many prescriptive grammar guides would consider that statement wrong. For instance, Towson University's Online Writing Support on "Usage - Pronoun Reference" says

A pronoun should refer clearly to one, clear, unmistakable noun coming before the pronoun. This noun is called the pronoun’s antecedent.

Then the site gives examples of "Errors" including too many antecedents, hidden antecedents, and no antecedents.

However, this approach addresses style rather than grammar. The site makes stylistic recommendations because students will often write sentences with confusing pronoun usage without any way to point or otherwise suggest what the pronoun refers to. Editors may impose such rules for similar reasons, avoiding bad writing by a blanket ban on usage likely to be misused. However, in terms of functional grammar (whether one understands what was just said or written without much thought), sometimes pronouns don't need antecedents to function well. For instance:

Mark called Mary's house all day, but she never answered the phone.

Absent some special context, she refers to Mary. There is no major issue with understanding that she refers to "Mary" rather than "Mary's house" or just "Mary's." Thus the sentence functions grammatically, despite the stylistic rule that Towson imposed.

Your example functions similarly. Most readers or listeners understand the sentence, including it, without much effort.