[Grammar] non-restrictive clause?

[hotapplepie]

Hi everyone!
I would like to ask a sentence from an article:
"The best part about Sunny Acres is that is was designed with the whole family in mind. For those jobs in the city, it is only a 45-minute train commute from the nearest station, Middlebury, a 15-minute walk away. For kids, Sunny Acres is close to elementary, junior and senior high schools, with safe walking access to each."

The blue font section is abbreviated from ",which is a 15-minute walk away", right?
I would think that is a non-restrictive clause because there is a comma before it?
But my grammar book says a non-restrictive adj. clause can not omit its relative pronoun---which, so I am very confused about its grammar.
In my view,it is like a adverb phrase modifying the foregoing word "Middlebury," but I don't know how to analyze its structure.
Can anybody solve my problem? I would appreciate it very much.
Thanks to your help!

 

[Raymott]

Hi everyone!
I would like to ask a sentence from an article:
"The best part about Sunny Acres is that is was designed with the whole family in mind. For those jobs in the city, it is only a 45-minute train commute from the nearest station, Middlebury, a 15-minute walk away. For kids, Sunny Acres is close to elementary, junior and senior high schools, with safe walking access to each."

The blue font section is abbreviated from ",which is a 15-minute walk away", right? Maybe. That's what it means.
I would think that is a non-restrictive clause because there is a comma before it? It's non-restrictive because it only adds additional information. It's true that there's a comma before a non-restrictive clause, but the comma doesn't necessarily make it a non-restrictive clause.
But my grammar book says a non-restrictive adj. clause can not omit its relative pronoun---which, so I am very confused about its grammar.
I'm not sure about that rule. But the sentence is correct.
In my view,it is like a adverb phrase modifying the foregoing word "Middlebury," but I don't know how to analyze its structure.
Can anybody solve my problem? I would appreciate it very much.
Thanks to your help!

It's a non-restrictive clause modifying 'station'. 'Middlebury' is interpolated, and hence takes commas around it, as in "This is my brother, Jack, who is helping me."
"My brother Jack, [who is] a happy man, is helping me."