Some of the questions in the N4 area that exercise the passive form require knowledge of use of particles with the passive.

It would be nice if this page also had usage notes as to which particles are used in the passive form.

For example:

ひどい　 吹雪ふぶき で　 、　 道 は　 通 行 止 め に　 された　

I cannot find why the は-に is the correct answer to this question

I think the passive used as honorific speech is missing here :)

I think this page having 5 grammar points is making too many subtle distinctions that are making the learning of this harder because they add mental burden for something for which the distinction is not very clear.
I suggest redoing this page ^_^'
This is how I would present it:

1/3 Direct passive
Someone or something is/was/will be A'd. Note: (In direct passive, the verb is always transitive)

Example:
一郎は花子に騙された。
Ichiro was deceived by Hanako.

2/3 Indirect passive
A is affected (often in a negative way) by B doing action C. Note: (the verb is not directly affecting A)

Example:
マイコーは太郎にビールを飲まれた。(negative)
Michael was annoyed by Taro's drinking beer.

高山さんは美人に横に座られてニコニコしている。(positive)
Literally: Mr. Takayama, having a pretty woman sit beside him, is smiling happily. (= A pretty woman sat beside Mr. Takayama and he is happy.))

3/3 Honorific passive
A does B. The passive form can be used as an honorific form, so A would be someone above the speaker (boss, customer, etc.)

Example:
彼が運転されました。
He drove.

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- Most examples are from DoBJG

ok, I've noticed something about point #3 - the whole separation hinges on the fact that the Agent (the one doing the action and marked by に/から) is not mentioned, and the example sentence for that point is 此の車は十年前に作られました。
But that sentence is an example of Direct Passive since it's using a transitive verbs, and it matches perfectly the description of my point 1/3 which is "Someone or something is/was/will be A'd. Note: (In direct passive, the verb is always transitive)" , so we could simply add the note to 1/3 that the Agent (the one that does the verb) can be omitted.
So the sentence I had brought as an example for 1/3 could be 一郎は（花子に/から）騙された。and the sentence currently in #3 would be 此の車は（ホンダに/から）十年前に作られました。(omitted Agent in parenthesis)

On that basis, making a distinction on 3 simply because something got omitted, considering that japanese already had the habit of omitting stuff (particles etc...) in many grammar points, seems excessive to me, a note on point 1/3 would be more than enough to remember that, I think :)